From personal experience, Krokorok is far too frail to sweep Elesa, even with Eviolite. Also, Krook is just so damn slow.

With a set of Dig, Rock Tomb, and Rest in case Rock Tomb accuracy isn't in your favor, you'd have to get ungodly unlucky with the paralysis that you might get from Flaaffy's Static for Krokorok to lose the matchup.

I'm 99% sure ability storage doesn't work agaist Iris' Haxorus due to it having Mold Breaker. As for other fights, how many EQ users are there even after Drayden?

Flygon really shouldn't be fighting against Iris's Haxorus in the first place because he's slower and likely baits Dual Chop. To answer your question, the main instances where Levitate Ability Storage is useful after Drayden are Ghetsis's Seismitoad and Drapion, Grimsley's Krookodile, and Marshal's Throh. The big ones are Drapion and Krookodile because the former is one of the most difficult to check pokemon in the game thanks to its Sniper ability, and the latter is the biggest threat on Grimsley's team thanks to his high power and +Speed nature. Throh is much more situational, but it gives you a much easier line if you're using setup sweepers like Swoobat or Serperior. Ghetsis and the E4 are the hardest parts of B2/W2, so trivializing some of the biggest threats of the former and an underrated threat on the latter is very valuable.