Well it's a combination of a lot of things: no animation cancelling, some animations quick while others lengthy and dangerous, occasionally poor hit detection, relentless enemy attacks in groups (they really weren't kidding with the Gothic influence), archers that can shoot through bushes and even tree trunks, automatic AI deflection of sword strikes (always with the second power attack!), input padding of parry and general unresponsiveness, inability to cast due to enemy attacks with no way to get out of the situation (hell in tight areas), etc etc etc.Drowners are the hardest ground enemy in the game because they are relentless (they gang up, and they double lunge), but they can only jump forward. I recommend dodging to the left and right instead of backwards. BUt all enemies on death march are really hard in packs.
It's death by a thousand cuts for the combat, which could've been great. I like it, but there's no denying the inherent cheesiness of some enemies. Whether you can overcome that makes no difference: cheese is cheese.