I've missed with 537 (usually every run I tried 537 I'd miss once or twice), on the legs, so you've just either had very little time as 490 ACC testing or you're quite lucky. 540 hasn't ever missed over hours.
Comps are way too varied for this to even matter. Doubly so if AST gets mega buffed in 3.06 or 3.1.
DPS leaderboards in general are pretty dumb, and I say this as someone who tries my best to do the most DPS I can.
