For assassin the talent increases all movement speed. it may not stack with sprint out of combat, but even if it doesnt I'd still pick it up for pvp to reduce range's ability to kite during combat.
I would rather the above (faster movement speed during combat) then have my speed increased while only in stealth... that would be fairly useless for pvp, especially during combat
Plus it makes sense that to remain unseen, you need to give something up. Speed would be that something.