Yes, there's stealth in WAR. It's pretty limited though; it is limited only to the 2 lowest armor melee DPS classes (one per side... and in both cases they are the most WoW rogue-like classes), and stealth drains their AP while active (your attack resource for all classes, though some classes have alternate pools for certain abilities) faster than AP regenerates, and has a cooldown of 2 minutes. (That's quite a lot in WAR. The most powerful abilities generally have cooldowns in the single minute range, though there are a few with longer).
It's also mostly there to let them have a role in large-scale PvP; their stealth helps them work with the tank classes to break gridlock when large zergs come together, and keeps them alive while they are crossing the no man's land in the center, else they'd never be able to kill the casters, which is their main role in PvP. And Melee DPS, in Warhammer's design are the main caster killers...