I would like to try and discuss the ways of dealing with super-kitted-up demon princes in the current iteration of the codex. In my local meta I seem to be encountering them more and more, and I'm finding less and less outs to dealing with them beyond hoping for a lucky cupped hands. I'd also like to see if there's anyway to play a good, competitive 2500 list WITHOUT the use/reliance of a slann. Lately my dice have been hating me, and if I'm not getting two or three spells off a turn, I ain't doin' anything. I've been playing against big Nurgle lists lately, with their poison, and -1 to be hit, but the most difficult thing is dealing with the demon prince and Epidimus.
For the unbreakable WoC nurgle DP, there is very little that can be done other than try and bog it down with a skrox unit (so they don't get stomped and last longer). Actually killing the DP is next to impossible since everything but SVs and OBs need 6s to hit and lizzie heroes will generally die before the DP in combat. Add in the ability to recover wounds through soul feeder or increase W & T with the lore attribute and the problem becomes even worse. A tooled up OB on cold one with S7 (GW + Voff) and built to last (1+ re-rollable & 4+ WS) might be able to do it but the problem is getting the DP locked in combat against him. The DP can fly and thus avoid combat if desired and with no war machines, killing a DP at range is not going to happen for lizzies. WRT Empidemeus, kill the character and the tally of pestilence stops IIRC. Scar vet cowboy with voff would do the job nicely. However, poison works both ways so skinks will also be auto-wounding on 4s with shooting (unless a higher roll is needed to hit). Life & light buffs (as well as heavens in a slaanless list) can help push the combat in your favour but even saurus with hw/s should give as good as they get against PB since they are cheaper and have more attacks. Flanking the unit with skrox also works since PB only have 1 attack each, thus minimizing the number of dead skinks giving up combat res. S6 thunderstomping from a flanking steggie will also help grind the PB down.
My view was based solely on the old book, not the latest codex, and it would make sense for it only to work for daemons.