It’s the skill that appeals to me the most but I feel like it will probably be really bad without crazy gear. Has anyone tried it with faction/crafted stuff or just whatever MIs apply to DE? It probably sucks to level with but being able to swap to it before ultimate would be nice. Also what class combo would be best and what would be the leveling tree for that?
Depends on what you consider ‘really bad’ I suppose. I didn’t really have any issues leveling with it. Get a decent Spectral War Shield ASAP. 
Drain Essence is really bad no matter how you build it. I made few builds, my strongest was cold DE, hitting 60+k per tick, but had shit casting speed, other variations had slightly more casting speed, but the damage was 40 - 60k. For comparison, lightning/cold AAR hits for 100k+ without debuffing, some ticks hit for 300k (debuffed).
With DE builds, I’d rather wait for FG. I even tried to mod the raw skill to be slightly better, but it either was OP as fuck or the same as now. 
Dreadwalker DE is okaysh. Keep in mind, all channeling spells suck ATM, so , don’t expect wonders of it.
What if someone really wants to play a build with channeling?
Anyway, when you get to Steelclap District and save Hyram for his shop, you can buy Ascendant Source’s that always roll with +% aether and vitality damage, and Fleshwarped Tome’s that always roll with aether to vitality conversion (that might help out in focusing on one of the damage types on the Drain Essence - namely aether)
Don’t care what these elitists old farts says, its all about having fun and if you wanna play with a channeling skill you should do so! 
My full Uruboruuk set Apostate is indeed at 40-60K per tick. I don’t know if this set is worth trying ? (Could you link me the elemental AAR build please ?)