The arena gates need to be made significantly more transparent. Too many times now I've thought I'd finished off all the healers only to have a whole group jump to full health because a healer was standing just inside the arena gate and I just didn't see him.
Sure in t1 it really doesn't matter but in 3 it can be the difference between an easy clear and a revive bill.
Why do you say that?
To me, that kind of thing is clearly a case of dying because of the view being obstructed, not by any of the normal rules of play. To me, that's just annoying. My knight is right next to the monsters by the gate, he should be able to see them, but I the player can't because of the area design... that's either bad level design or bad game design, and definitely annoying.
In-game reasons for being unable to see might be different (like the blue bomb clouds, or if they introduced a monster that fogged an area up). But this isn't an in-game reason, it's a game-design reason.
(Although, actually, I find blindness effects quite annoying in any action game anyway, and would invest in the best possible protective eyewear if there was such an in-game hazard. But it would feel less unfair and so be -less- annoying.)
Through fault of my own, I have chilled by the gate, to not realize that an enemy was there too, just wailing on me and killed me. Would it be nice to know he was there or not? Sure. Are there other areas like this? You bet. Should it be made transparent? No, in my opinion.