It just seems arbitrarily restrictive on the face of it, is all.
If there's no choice
within your tree of choice then I'd agree; but from the sounds of it I don't think that's going to be the case. You'll still have choices to make and ways to differentiate your character. And at higher levels you
will be able to invest in hybrid builds to a similar extent as you're able to now. I don't see the problem.
Incidentally, I'm one of the few people who think that the dual specialisation system was one of the worst developments in the history of WoW. If there's anything that stripped the function of the talent system in contributing to the identity of your character, it was that. And most people loved it. Blech.