not sure about all the skills of your class but if you are talking about the detonator you throw on some1, its pretty useless vs an assassin. I force shroud half a second before the explosion and laugh out loud XD especially when I have more then one on me lol
Assassin is the only reason? You can't negate a power from being useful by just having a counter class. That's like complaining that a healing spell sucks because a marauder can choke you while you cast it.