Normal difficulty.
Have a sneaking suspicion the boss battles are gonna be pure torture on Hard difficulty if you don't abuse one or more homebrew game mechanics.
I hope they will.
No shoving bosses though. I expect they will see through greater invisibility and possibly sneak tactics if they have tremor sight.
I will have 2 healers and some burst damage though, so it will be a fun time.
Just hope there is room to hang back and burn down the minions first.
A near TPK is still a win and usually the most fun.
Now I'm having World of Warcraft flashbacks. (39 / 40 down and the lone Gnome blinks around and lands the final blow).