Allow me to disagree, too. Corner trick represents, like Sylph said, the ability to shoot out of cover. Moreover, while removing it does not equal total removal of tactics from the game, it does remove a lions chunk of it. Let's analise your proposed tactical points:
1: Shooting enemies out of LOS, while a viable tactic, incurs accuracy penalty. Consider the folowing situation:
B
@#####
The knight will come into view within one or two moves. If corner trick is removed, it will then proceed to fire immediately. This means that the player has only two shots at most, each with additional acc. penalties, to make before he starts to get damaged - and that's almost never enough. And, considering that all B's are telepathic monsters (they know where you are even if they don't see), the player will have no way of outmaneuvering the knight - so he WILL get damaged, no matter what he does.
2,3: Requires some RNG love, so it's not really a tactic per se.
4: A barrel blast is never enough to kill tougher enemies. So it's the same as 1.
Also, consider this points:
1. Removal of any tactical tricks the player has, will, ultimately, only make the gameplay poorer.
2. The corner trick is deeply ingrained into the mind of DoomRL players - suffice to say it is featured in both FAQ's I have read as primary advice for beginning players.
All in all, I think that if such a change is to be made, a vote is in order.