I second this, sure it has "bad defensive typing but honestly most people should have something to check special attackers, like Chansey or Blissey. Yeah, Avalugg totally cripples Mega Chomp. I ran a Curse+Gyroball set. and practically the same EV spread. Worked wonders on the battle sim.
I don't really want to be 'that guy', but given how commonplace mixed M-Garchomp is, and the fact that only CB and SD Chomp don't carry Fire Blast, Avalugg can hardly be considered something that 'cripples' it, with rocks up, it's not even a check.
0 SpA Mega Garchomp Fire Blast vs. 252 HP / 4 SpD Avalugg: 338-398 (85.7 - 101%) -- 12.5% chance to OHKO (OHKO's if rocks are up.)
Even if it is a banded Chomp:
252 Atk Choice Band Garchomp Stone Edge vs. 252 HP / 126+ Def Avalugg: 162-192 (41.1 - 48.7%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
It's 2HKO'd by Stone Edge if rocks are up, meaning that it can't switch in on it. Even if they're not up, it doesn't enjoy taking either of the two moves at all. Not saying that Avalugg is a bad wall or anything, I just don't think it has much of a place in the higher tiers, given that it's atrocious typing severely hinders its ability to stomach near any hit, and it's primarily outclassed by other defensive tanks in both OU and UU.
Anyway,
I would definitely start looking for a bulky Water-type or Rock-type. As it stands, your team is horribly weak to anything Fire-type or Dark-type, having no switch ins whatsoever; most notably Banded Victini and Honchkrow. V-Create decimates your entire team, and nothing wants to switch in on Honchkrow, especially if it's a sub variant. I'd recommend running a Rhyperior.
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Trait: Solid Rock.
Impish Nature (+Def -Sp.A)
252 HP / 4 Atk / 252 Def
-Stealth Rock
-Earthquake
-Dragon Tail
-Rock Blast/Stone Edge.
And of course, Slowbro and Cohagrigus, which were stated somewhere above, also work very well.