I don't know if this is the sort of forum where noobies get flamed for accidentally rehashing old discussion...but here goes nothin.' ;-)
Firstly I think DoomRL is genius and shockingly true to Doom. I haven't been this addicted to a computer game since I played Doom the first time around. My kudos to all involved. But there are some elements of level design which are a lot different from the original. One of those is teleporters.
As of right now I don't see much point for teleporters in DoomRL. In Doom they usually took you to some new, exotic place you couldn't get to otherwise, perhaps with goodies. In DoomRL they take you to some place you can already go to where you'll possibly be mobbed by monsters and instantly killed.
I don't know too much about how the engine works at this point, or the history of teleporters in DoomRL, but would it be possible to have the teleporter take you to a separate, subarea of the level? (i.e. basically a smaller mini-map.) If not, how about an area that's walled off?
Sure, there's still the possibility of being mobbed, but if some sort of goody is guaranteed, it might be worth the risk. (a soulsphere, a bunch of ammo, an exotic if you're really lucky....whatever)
If nothing else, teleporters should at least go to another teleporter to act as a shortcut through the level.