Can be true, I think the secret to the assassin is not worrying about getting high numbers of shrouds. Put 1 on and use it immediately seems to work quite well tbh. Then again I've only seen the assassin at Heroic, I could see them falling behind at paragon.
"Falling behind" is certainly one way of putting it. Much like how you could say someone that was currently dead was "Not breathing very well". Paragon is where you really see how bad some strikers can really become and just how big the gulf is between well designed ones (Rogue, Thief, Slayer, Barbarian and such forth) and poorly designed ones (Vampire, Assassin).