Set's healing on average is 250 per turn(1500/6)
Gaia awakened has a heal in the form of a regen that has an average heal of 171per turn(400*3/7). But Gaia also has a damage cut, along with a Cover+Nullify skill which means overdrives do 0 damage. The damage cut and damage negation over the same period of time would "block" way more than the extra 79 heal per turn per hime from Set.
Only reason you'd prioritize Set over Gaia is for affliction resist AND affliction cleanse which would be dependent on content.
quick question. do fire rag supposed to be able to use its overdrive 2 times in a row?
First follow kyc992's advice and get your assault skills in your weapon grid up. That'll help a lot. If you're doing 50% more damage, you might not feel the need to rely on healing as much as you currently are. Gaia's got a self heal, Azazel has energy drain and cybele also has a self heal, not to mention Joan's regen. Set is overkill and takes the place of a strong striker. Gaia's damage cut and block are stronger party 'heals' than Set's though they do this through damage avoidance/mitigation (a priori not after damage done). The only one without any self heal is Hastur. For now you can live with potentially her going down.
Dejnov.
Gaia's party regen is from Awakening and lvl 75, but prior to that it's a self heal.
Also forgot to mention, the regen from Gaia does not stack with Joan's. The damage cut however does. You can effectively rotate regen for better turn coverage. Also you can effectively block overdrives by using Gaia's other Earth+ to negate it once, then use bothh Gaia's Genesis and Joan's Voice of the Gods for an 80% damage cut. With 40% AB attack down frames and 80% damage cut, you effectively cut boss's damage down to 12%. Not counting boss's regular attacks, the party regen you have should be more than enough for you to tackle bosses for a decent amount of time. But the regular attacks will still eventually wear you down, as explained by Shieun's "This game is designed in a way that the boss will eventually outdamage your healing cooldown or the time limit is going to mess you up".