so what teams does this realistically fit into again? I'm struggling to find a way in which it isn't outclassed
I admit it's probably outclassed, but I do think it is worth considering how it got better or affected the viability rankings.
For these comparisons, I'll be looking at him without an item boost, so a lot of the +1 KOs will hold true for a Choice Band set, though they will more likely be on the switch without the boosted speed.
Most immediately, this thing might put Mega Tyranitar out of whatever job it still had. It hits the exact same speed tier (outspeeding Greninja at +1 Max Speed), while having the utility of an item for power, status buffer, or minor recovery in Leftovers. Doesn't have nearly the same bulk, but T-Tar's typing ultimately negated most of that in practice.
+1 252 Atk Mega Tyranitar Stone Edge vs. 0 HP / 0 Def Mew: 291-343 (85.3 - 100.5%) -- 6.3% chance to OHKO
+1 252 Atk Tyrantrum Head Smash vs. 0 HP / 0 Def Mew: 348-411 (102 - 120.5%) -- guaranteed OHKO
Even with no item, Tyrantrum achieves better damage output, and that damage is almost ridiculous enough to forego coverage besides EQ and maybe FF for specific steels like Ferro.
+1 252 Atk Tyrantrum Head Smash vs. 252 HP / 88+ Def Ferrothorn: 117-138 (33.2 - 39.2%) -- 10.5% chance to 3HKO after Leftovers recovery
+1 252 Atk Tyrantrum Fire Fang vs. 252 HP / 88+ Def Ferrothorn: 272-324 (77.2 - 92%) -- guaranteed 2HKO after Leftovers recovery
With SR, there's a good chance at +1 to 2HKO Mega Slowbro, the single bulkiest Physical mon in OU.
+1 252 Atk Tyrantrum Head Smash vs. 252 HP / 252+ Def Mega Slowbro: 163-193 (41.3 - 48.9%) -- 80.1% chance to 2HKO after Stealth Rock
The thing that makes Tyrantrum a notable DD Wallbreaker, to me, is that Head Smash's ridiculous power almost means he never needs to predict once he boosts. Head Smash might not 2HKO all the resists, but it can knock off enough health that a coverage move will. Tyrantrum doesn't match up the best against offense, but against Stall, or balance, that one boost gives him what he needs to make them cry.
Obviously, his Special bulk and typing don't do him too many favors, but his physical defense is usable enough. His typing and Physical Defense at least mean that mons like Talonflame, Azumarill, Pinsir, or Mamoswine can't revenge him at +1 with their priority without some notable damage.
252+ Atk Choice Band Talonflame Brave Bird vs. 4 HP / 0 Def Tyrantrum: 102-120 (33.3 - 39.2%) -- guaranteed 3HKO
252+ Atk Choice Band Huge Power Azumarill Aqua Jet vs. 4 HP / 0 Def Tyrantrum: 103-123 (33.6 - 40.1%) -- guaranteed 3HKO
252 Atk Aerilate Mega Pinsir Quick Attack vs. 4 HP / 0 Def Tyrantrum: 42-50 (13.7 - 16.3%) -- possible 7HKO
240 Atk Life Orb Mamoswine Ice Shard vs. 4 HP / 0 Def Tyrantrum: 148-174 (48.3 - 56.8%) -- 89.1% chance to 2HKO
252+ Atk Dread Plate Bisharp Sucker Punch vs. 4 HP / 0 Def Tyrantrum: 144-171 (47 - 55.8%) -- 78.5% chance to 2HKO
Again, he's nowhere near levels like Mega Altaria or Metagross, but it's something at least.
I see Tyrantrum (should he be ranked) ending up around Mega T-tar's rank, maybe one rank above because he saves the Mega Slot.
