Levelers like Coralhelm Commander are getting counters added to them even when they reach max level. This is affecting performance because it ties up the AI's mana for no reason at all (very annoying if it's meant to be counterspell mana).

EDIT: Also, Coralhelm Commander in particular just had a silly situation for me: The AI didn't attack with it for reasons unknown. It started the turn as a lvl 2, so it had flying and could attack. The AI passed combat without doing anything, then tapped all 4 of it's lands to get the commander to lvl 5, which was both silly (because it could have done it before attack and attacked) and superfluous (becuase it only needs lvl 4 max). It chose to do this instead of playing any of: Jolting Merfolk , Manta Ray or keeping mana open for either Mana Drain or Confound , it had all of them in hand. No idea what is up with that, but I do hope Coralhelm Commander leveling is available pre-combat.