1) environmental hazards are either part of the challenge or avoided with high body control.
One of the more annoying chapters for me was toward the beginning before I had the opportunity to put points into anyone's body control. The chapter with the crypt lice and the stalactites, specifically. The lice weren't a problem, but using magic had a nasty tendency to knock down the stalactites on top of my characters, and the camera made it impossible to tell where they would fall. Very annoying, and there were a few other chapters like that where I couldn't help but feel that the environment cheapened the otherwise solid tactical elements. Especially the stage with the poison vapor that acts like a time limit. What a middle finger that one was.
As for 2, I know that it's a plot element, but the game's habit of undermining your strategies is incredibly annoying. For example, there's a chapter toward the end that takes place as a flashback and you subsequently lose all of your character progression for that one chapter. The fun of games like Blackguards should be the brutal difficulty along with mechanics that dare you to find a way to beat them, but the curve balls that force you to play the way the game wants you to really ruined it for me.
3) Saves work OK. There are manual saves, quick saves, autosaves and "this battle" saves. You can't save IN battle but I'm fine with that, it would be greatly exploited otherwise possibly nullifying risk and planning.
At release you weren't able to save between multi-stage fights, meaning losing one fight in the arena (and many other multi-part fights toward the end) knocked you all the way back to the beginning. So much frustration. But yeah, I've heard that they fixed that in a patch, and mid-battle saves would definitely cheapen it.