Found it very easy as destro, because of the mana and self regen. It's ok to let your pet die, just use demonic gateway and summon him again and again. You can do the whole fight not healing your pet a single time.
As a nice tip (that works for every boss, but especially low-hitting ones), if you have a huge Soul Leech shield on your pet and if your pet has Void Shield up, any fully-absorbed hit won't consume a shield stack, but still will be reduced by 60%. So if your Soul Leech shield is high enough to last, your pet can stay with the 60% Void Shield dmg reduction the whole time.