I checked, mines not procing for some reason.

TL; DR version: I can confirm that DK sustain is markedly worse; even when I'm just parsing on the 21mil target dummy. I tried running the mag DK build I ran before the last update and I completely ran out of magicka about 45 sec in to my parse.

Long Version: It's very much worth noting that my mag DK is built to have a generous amount of sustain. I wear False God's Devotion and Z'en. False God lowers the cost of my magicka abilities, and one of the set bonuses of Z'en is extra magicka recovery. I also parse with spell power potions and "parse food" (i.e., Ghastly Eye Bowl). Suffice it to say, I was incredibly surprised that I ran out of magicka so quickly. It's even more surprising when you also consider that the 21mil dummy gives some pretty generous sustain buffs (i.e., Worm, a shard every 20 sec, and 100% War Horn uptime).

I couldn't, however, verify how often Combustion was proccing. I tried inspecting my resource events in CMEX, but it wasn't listed. I saw some occasional procs listed as 'Unknown', so perhaps these were Combustion?

Nonetheless, I think it's safe to say that the Combustion passive was 1) nerfed too hard and 2) probably not functioning as often as it's currently designed to.

P.S. Not to be harsh to the developers, but it is a bit ridiculous that I can't even sustain a mag DK with *2* sets that provide generous sustain. This combination was more than enough to sustain an entire 21mil parse before the last update. Now I can't even make it more than a minute before all of my magicka is gone. For the record, I've never been a Talons-spamming DK, so it's not like my magicka is being drained by a costly ability. According to CMEX, my biggest resource drain is Whip--as was the case before the last update. So the overall ranking of the sources of my resource drain hasn't changed; just my overall sustain. And I hope it's clear what the culprit behind that is.