Though I am a faithful servant to Legacy Burn, there have been times over the years when I've put the deck down. The most memorable period for me was a few years back, when decks like OmniTell and Sneak and Show ran amok on the Open Series and Invitationals. Even a glutton for punishment such as me eventually got sick of getting killed on the third turn after my opponent lead with a Turn Zero Leyline of Sanctity, leading to dalliances with mediocre decks like Jund and Jeskai Delver. Soon enough, the booth beckoned and I no longer had to worry about such things.
However, things have slowly but surely shifted in Burn's favor over the last year and change. Part of it is a seeming commitment from WOTC to keep cranking out Legacy-level creatures, meaning one can now build a deck composed almost entirely of white creatures and hang with combo decks. Partially as a response to that, and partially because the stock list had become much more refined, Elves became a big player in the format, becoming the most representing combo deck at most events. Because creature removal is a more reliable form of interaction against Elves than soft permission like Spell Pierce (as well as in the mirror and the semi-mirror), the many shades of Delver have tilted their decks more and more towards the former than the latter.
With the printing of Treasure Cruise, all of this has ratcheted up even further. Before, Delver decks had to keep more powerful decks like Esper and Miracles off-balance with soft counters to prevent their powerful action from resolving; now Delver decks can overpower the control decks by drawing a ton of cards. Since Treasure Cruise promotes proactive cards (just cast your stuff, gas back up, repeat), Spell Pierce has been on a significant decline in recent weeks. The games are now about Treasure Cruise, and Spell Pierce is neither efficient at fighting Treasure Cruise, nor is it a card you want to draw once you resolve a Treasure Cruise of your own.
The effective swapping of Spell Pierce for Treasure Cruse helps Burn immensely, since Spell Pierce is the best card many Delver, Esper, and other Blue decks bring to the table against you. Treasure Cruise also promotes capping out on fetchlands and cheap cantrips, which is a serious boon for a Burn strategy with Eidolon of the Great Revel. Though Burn hasn't had a big performance since the printing of Treasure Cruise, it was on an upward trend over the previous months, and I believe Treasure Cruise generally makes the format weaker against Burn for the reasons I mentioned.
Aside on Treasure Cruise in Burn
I've been asked about putting Treasure Cruise in Burn quite a bit. It makes sense, since the deck reliably fills up the graveyard, and drawing more Bolts seems really sweet. I am skeptical, because every time I've touched another color, the losses to Wasteland (alongside the minor inconsistences one would expect by splashing) have more than outweighed the upside. Treasure Cruise is an entirely different animal than Brainstorm or Ponder in Burn, however, so this stance requires some reevaluation. Still, if one wanted to go down that road, I think the U/R Delver build does a much better job of being that sort of deck, since it cares much less about getting hit with Wasteland than Burn. I will offer up an untested thought experiment build of Treasure Cruise Burn, for the curious.
Over the last few months, I've been noticing a weird trend among Burn decks on the Open Series. For the first time that I can recall, something of a "stock list" has appeared. For years, the lists I've seen and covered have been all over the place, but now I see nearly the same 60 cards each time. Coincidentally, it is very close to the list I've been advocating for a while now.
I believe I see a 3/2 split on Searing Blaze and Sulfuric Vortex more often than a 4/1 split, and the fetchland/basic land split is all over the place, but otherwise there appears to be a consensus on what the maindeck is supposed to look like.
I won't pretend this is an exact science. The fetchlands help with Grim Lavamancer, Searing Blaze, and deck thinning, but come at the expense of the aggressive matchups and Stifle. This feels about right to me, but I could see the numbers tilting up to two in either direction depending on what you prioritize. I think less than eight or more than twelve of either land type is a mistake, but I will accept any number within the margins. I've played 21 lands in the past when I was playing numerous Sulfuric Vortexs main or things like Figure of Destiny, but I think twenty is appropriate in this build.
They are generally great when they're in your opening hand and are generally poor past that, but the upside is the worth the cost, and the quality of potential replacement burn spells falls off a cliff once you get past the ones that are already in the deck. Goblin Guide is a great rate, but you should feel pretty liberal about boarding these out, especially when you're on the draw. I had my doubts initially about Eidolon of the Great Revel in the maindeck, but it's great against nearly everything that doesn't play Tarmogoyf, and even pulls weight in the mirror match. Grim Lavamancer is more "utility" than "beater," but still gets work done on clogged boards. He is your best weapon against creature decks lacking lots of removal, like Elves and Death and Taxes. I'm not opposed to boarding out all creatures in matchups where you have eleven reasonable cards to bring in and you expect heavy resistance to creatures, but that's an extreme measure, and you should err on keeping all of them in on the play in almost all matchups.
The only fluctuating slot is Searing Blaze vs. Price of Progress vs. Flame Rift. All the other cards are staples, and you can only fit in two of the remaining three assuming you aren't willing to cut creatures. Searing Blaze is live against a huge portion of the field, and Price of Progress is at least good against most decks. More importantly, many of the decks in the format are aggressive, raising the opportunity cost of Flame Rift significantly. I've played upwards of three Sulfuric Vortexes maindeck at certain points, but the popularity of Abrupt Decay alongside the speed of the format makes it a low priority for me at the moment.
Trading one-for-one when your deck is full of Lava Spikes is a recipe to lose the game with your opponent at seven life. As such, I have no interest in Red Elemental Blasts, Shattering Sprees, or other similar cards I see scattered in other people's sideboards. The only things I want are things that deal damage, or cards that lock my opponent out of the game entirely.
Searing Blood is for the obvious creature matchups, and it even does work against Esper Deathblade and other control lists flush with creatures (like Shardless Sultai, assuming that's still a thing). Ensnaring Bridge is a lock against a number of decks, but don't go overboard bringing it in. Elves has Abrupt Decay, Death and Taxes has weird workarounds like Flickerwisp, and Esper lists can still beat you with Jace, the Mind Sculptor. I only like bringing it in against Reanimator, Sneak and Show, and Delver builds that are both slow and have very few ways to kill it (like Jeskai and Temur). U/R Delver is too fast and can burn you out anyway, making Ensnaring Bridge poor against them.
Smash to Smithereens is for Stoneforge Mystic decks, Chalice of the Void, and various MUD/Affinity decks, and the other Vortexes are for control matchups like Esper Deathblade and Miracles. The Flame Rifts are the oddest card in the sideboard, but they help in the combo and control matchups and are something of a catch-all. The maindeck contains both Searing Blaze and Price of Progress, both of which can be dead, and if you ever find yourself in a matchup where you need to cut one or both and have nothing else to bring in, Flame Rift is always an option.
It is an open question if you want access to Relic of Progenitus in the sideboard. It does good work against Treasure Cruise decks at a low opportunity cost while doing work against other decks in the field. I don't think Treasure Cruise itself warrants specific attention, but if you are worried about other graveyard strategies, I think Relic is a fine choice. I wouldn't cut anything from the sideboard except Flame Rift to make room, and four copies seem excessive in any case.
Common Decision Points
Since Burn is about assembling a critical mass of spells, and trading resources is anathema to the strategy, mulligans are very punishing, and you are better served keeping sketchy hands rather than fish for a better six most of the time. The thresholds for mulligans are:
1) One-landers with numerous 2+ mana spells, or one-landers with 2x Fireblast that lack significant upside (like 2x Searing effects vs. Death and Taxes)
2) 4 land hands without a creature and without multiple high-upside spells (Prices or Searing effects in their best matchups).
3) 4 land hands that can't kill a creature in a matchup where that matters (Stoneforge Mystic, Elves, etc.)
4) 5+ land hands regardless of composition (barring extreme outliers like 2x Grim Lavamancer 5x Fetch Land on the play vs. Elves).
When it comes to playing the games, most things will be fairly straightforward. Be mindful of mana efficiency, and in the blue matchups, Daze and Spell Pierce are the biggest swing cards. Fail to play around them appropriately and you will certainly lose; with good navigation you can usually deaden the impact of those cards. I wrote an article a few months back that will serve as a good refresher course on the tactics of doing this.
On a strategic level, the most common mistake I see people make is killing non-essential creatures. It is correct to kill a Stoneforge Mystic that will put a Batterskull into play. Otherwise, it is generally a mistake to be killing a Delver that's hitting you for a few points. Remember what I said before about trading one-for-one, and in any event there's some upside to leaving opposing creatures in play when you have Searing Blaze in your deck. A good shorthand for using a Bolt on a creature is, "If you are unsure if it is correct, don't do it".
Legacy is a huge format, and some matchups for Burn are hopeless. If you catch the wrong end of the pairings, you could be facing Turn 1 Ionas and Chalice for one, and you will have a brief tournament. But with the right pairings, Burn is a robust deck with positive matchups, and I believe right now the field is well above-average for a good Burn pilot. Since I'm covering the Grand Prix, unfortunately I can't play, but if I could, I would play something very close to the list I posted in this article, and likely, I would just play the 75 above. Best of luck to all my kindred Burn spirits and if you see me in Jersey, don't hesitate to come up and say hello.