The difficulty in any RPG is is always reliant on player knowledge.
The game is still fresh and new enough for me that those encounters still happen where I'm getting surpised - both myself and in game. Just the other day I encountered Grym for the first time, and my party literally melted.
And, if you and/or your party gets ambushed, you're in for trouble. Not having the first turn is *huge*, especially on Tactical, because the enemies don't miss unless they roll 1's.
Fail to notice the Githyanki at the end of Act 2, for example and just marching into their ambush? You get your teeth kicked in, however awesome you are.
But, but the same token, I know where they are hiding now, and even if I fail that perception check, half their team is slaughtered before they get a turn in. So that suddenly becomes easy, even if I struggled with them before.
