If I recall correctly, someone said that there is only 30% chance he'll make the somersault, not sure though :s (the Blood and Night elves in WoW also have a x% chance to do a spin while jumping)

Lar said during the presentation that the Dragon Slayer is very agile, maybe if we get some background info during the game, it'll be explained more. (Maybe the Dragon Slayers are a kind of mutants like Witchers)

I personally prefer a somersault in full heavy armor while wielding a 2-hander than having to walk along a fence cause I'm wearing too much to jump. Heck, when playing Oblivion I can even jump over the watersurface in full Daedric and a Warhammer, somersaulting in heavy armor is at least somewhat more believable laugh

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