Hmm. To say you're attempting a pistol-only YAAM on A100 is pretty ballsy. I can't give you any sure-fire advice for all Vile-Mancubi packs, but this is likely what I would have done in your situation:
- From the center of the map (which I imagine you were near before ending up in that awkward position), keep out of the Mancubi's range, slowly luring him away until reviving from the Vile doesn't occur.
- Then, row by row, I would shoot blindly some 10-12 shots and listen for Vile noises. After hearing the Vile, killing him off-screen shouldn't be too much trouble.
- At that point, finishing up the other Mancubi ain't too bad.
Since you're going pistol A100, I would highly recommend prioritizing SoB over Fin->WK. Don't expect to be as lucky with power mods, and you'll get your WKx2 eventually. If you think a unique pistol's gonna show up...well, that takes the fun out of pistol-only, doesn't it?
It is important to remember that revived monsters (either by N! respawn or Viles) have the same "frozen time" that affects them at the beginning of a floor. For Mancubi, it's a little longer than the typical monster, so I wouldn't worry too much about their revival for reasons other than ammo conservation. If anything, you could try to knock-back the guy into lava and hope he dies there.
Running gets the best use out of pistol-only by scouting out enemies. One possibility would have been to turn on your tactics, then make your way to the right via side-stepping to check out what you're up against.