Well, Master Shadow in itself is a very worthless tree, imo. I say that only because I have that tree on my belt, so I've used it before.
It is great defensively, but it lacks any offense at all. It's only move is Ghost Strike. While it does a good bit of damage (400 base), it's not enough to quickly dispose of a target. Instead you can only rely on it as a last strike to finish someone off.
The only plus to the MS tree is Impart Invisibilty. Vanish is very handy, but takes too long to recharge.
Overall, I think the timers are fine as no one can really overwhelm anyone unless they are substantially lower leveled than they are.
But these are just my thoughts.