I main a Demon Avenger, I'll admit, they're pretty inconsistent due to Demon Frenzy but they are pretty good until maybe around after Magnus (if played properly). They do indeed survive longer due to Nether Shield's healing. I'm gonna say Dark Knights are better than Demon Avenger mainly because of FInal Pact. Survivability on Dark Knights is insanely impressive if you back it up with Buff Duration increase. In other words, Dark Knights can survive longer than Demon Avengers and you're given invincibility as well. (I'm lazy to train on Dark Knights, since I been playing my Demon Avenger longer and I only needed at least 140 on my Dark Knight.)
