I actually prefer to kill him damageless with a cateye build which makes it too easy. The weapon choices don't matter that much. It can be bfg/plasma/rocket or whatever that can hit from big range as an elephant gun, it doesn't really matter.
The only true caveat is that you should try and have enough ammunition, plus as much speed as possible on the char (tactical boot & armor for instance and a HR trait or even more movement speed if possible) and perhaps an EE trait point or 2, to actually make hits from large distance. Easier done in AoMC ofc.
Supposedly Cyberdemon had a bigger sight range than the doomguy, but cateye with INT2 actually reverses the roles.
With the above requirements you just run around the level trying max distance shooting and running again. If you do it correctly then Cybie will never even manage to throw a rocket.
Done it twice or thrice till now, it does work at least in 0.996 it worked. I find that method even easier than dodgemaster but maybe it's just me.
Also, if you get cornered due to the layout and the positioning "run" to get away fast enough and raise the distance. Use medpacks for fatigue for more running if needed.
PS: It's obvious that antigravity boots, and/or phaseshift/malek's armor make the cyberdemon head (as well as the masterminds), a walk in the park with the above build.
