Arials get fly, yes, and wingsweep is sweet for characters that can't see hidden as it gives an opportunity to bring thieves, assassins, rangers, and Outlanders out from hidden. This is overly awesome for a rager against assassins. It's a different kind of niche than swiftstrike.

Stoneskin timer is less relevant at hero. You can get stoneskin for free for what, a 1/3 of a char's hero life? Consider a thousand hit points - stone skin adds on about 333. I consider that better than a few swiftstrikes. Again, swiftstrike is really only useful when a high avg weapon is used against a non-protected opponent.

I've argued for dark-elves to get something extra. A short levitation timer would be nice (can't use it in combat though).

Swiftstrike is just flashy, that's all. And again, you're seeing it on a build that maximizes swiftstrike.

Elves (except paladins, imo) in general needed something to help out in general combat. Evade and swiftstrike have helped.