Plox is definitely Tier one thanks to DCE. The ever-so-dreaded constant and fast power locking is just going to ruin the meta-filled Uxie, Claydol, Unown G, and Crobat G.
I personally don't think Donphan variants will be Tier one. Donphan isn't too great, since Gatr can easily tear it down with weakness. Maybe tier two or tier 1.5, but not tier one. Machamp isn't tier two either, since HGSS has PLENTY of evolution cards. I'd stick in Feraligatr in tier 1, seeing how he can be constantly doing high damage pretty quickly. Jumpluff in tier 1.5, since it has great speed but a few bad matchups, and Charizard variants in tier two. So, I would think something like:
Tier one:
-Flygon variants
-Feraligatr variants
-Dialga G variants
-Plox
Tier 1.5:
-Donphan
-Jumpluff
-Garchomp SV (non SP)
-Porygon-Z (depends on Dialga G/Spiritomb popularity)
Tier two:
-Gengar
-Ampharos
-SP variants
-Charizard
EDIT: Plox is short for Psychic Lock, the name of Gardevoir SW's Power-locking attack.