second one is a no-no as you can destroy valuable equipment by barreling places you havn't seen.
Oh, i destroyed pack of 20 plasma cells... Better would suffer damage of 16-21, but save my precious cells that are not even enough to kill AV. No matter that if i don't suffer this damage, i won't need this "valuable item".
There are no valuable items in this game. Point.
That does indeed work, but you can also replace that with:
###########
@#........#
.+.....i..#
.#h.i....h#
###########
In which case your point is moot. Sure, it does reduce the chance of fighting everything at once but there still is a chance.
Of course you always have a chance to die in this game. We can't create Perfect-Uber defence FROM EVERYTHING in this world. But at least we can reduce the chance that something bad will happen.
Also, let's say you did encounter a situation like the one in your quote. Once you'd killed the imp, you'd have to either
A. Close the door, but that's not too smart unless you're on low HP
B. Move down, take over 10 HP worth of damage.
And my original arguement comes up again.
A is stupid. Just stupid.
B is even more stupid than A.
Your next moves would be:
############
@.#......i.#
../...h...h#
..#..%.....#
############
#############
@..#......i.#
.../...h...h#
...#..%.....#
#############
##############
....#......i.#
@.../...h...h#
....#..%.....#
##############
And guess, you are now the king, you have door, through which you can fire to find enemies that are behind it. In our case you can kill 2 Sergeants without getting hit. Listen to the sounds of the monsters, that's why i changed soundbindings for every Former monster to different sound.
Again, that works but it requires a barrel and a gun. You can't push barrels through open doors (Last time I checked) so unless you actually had one in the room with you (And the room would have to be big enough for you to get out of the blast radius) this wouldn't work. It's basically countering a coincidence (Imps and sergeants behind a door) with another one (Barrel in your room, room is big enough for you to hide from the blast).
Barrels are quite common. You don't need to push it through open door(and it's impossible because it's just impossible, and because it's stupid to open door with barrel near you), you just need to blow hole in this wall to get rid of this potentially dangerous place, and in addition to hit anything that was fool enough to hide behind it.