Yeah, and it really comes down to two issues:
1. How insanely easy it is to counter, block and avoid attacks. Enemies telegraph their attacks very slowly, and the window of opportunity to counter is big, so you'd have to be barely paying attention to even get hit in the first place.
2. The abundance of hit points, which is a big problem since it's so easy to avoid taking damage. You start out with like 5 or 6 squares of health, which means that you could fuck up several times before even being in danger of dying in combat.
So basically, it's hard to get hit, and getting hit doesn't mean shit. Ideally, as an Assassin, you would have to rely on agility and craftiness instead of simply being an unstoppable killing machine that can withstand more damage than a tank. Ubisoft should at least pander to people like me and offer a hard mode where you only have a couple blocks of health.