Heroics are crazy hard for solo multiboxers. Mostly because our gear is "on par" with the instances (or below), whereas in TBC we would run around in s2/etc gear which was 20-30 item levels above the instance gear. It does get easier with time -- I started heroics last week, died 10+ times in UK first boss and dozens in other heroics. This week I cleared UK, Gundrak, and a few others with much fewer wipes (my gear has gotten a lot better, focusing mostly on my tank).

Sadly I just don't feel like running heroics tbh as a multiboxer, they still are crazy hard, I wipe a lot, and usually I get something that nobody can use

I would recommend perhaps running heroics SOLO, I've been doing one a day with my prot pally slowly getting geared up (also ran naxx10/25 and VoA). Will do the same with my shaman(s) too next week. Gear definitely helps a lot.

Wrt moorabi specifically, definitely try to interrupt his transforms as much as you can. He does a lot less damage in troll form. It is a DPS race, but you can't forget to heal. I downed him with 3 ele shamans (+prot pally + mage) and would rotate between DPS, lhw on tank, and all chain healing after quake. I just respec'd one of my shamans resto, to be honest I'm finding it worse than 3 ele shamans but I'm going to play with it for a day or two and see if it improves as I tweak macros and my attack sequences.