Question about boosting Hellverse's damage

Crylix

So 2 days ago I got my hellverse from that christmas event and I was wondering which of the two following skills will benefit my damage, both for pvp and (mostly) pve.

I've attached a screen with his stats below. Do you think 100% combo rate (8th skill) or increasing assaulter's attack by 15% (doesn't say for how long, I suppose 1 turn duration, 9th skill) will buff his damage more?
I can also make my main T1 based, to start boosting his damage from the start. Also I own Isane, and can make her also skill first turn, however it's either main or isane because I don't have fury stones for both. Isane skills every turn, so using fury stones on her will only make the boost come 1 extra round (1st round, but for whole team) while on main it will be twice because I will skill 1st and 3rd turn on Ryoka & evil spirit, and void sooner or later.
My zanpakuto is Katen (until I get Kyoka which is still months away, so note that I get that extra crit chance/damage every other turn.
Whole team at this point is: Kirinji, Isane, Main, HVI and H.Ichigo (tavern), if that helps anyhow. No further plan to top-up.

theunknown404

I would prioritize Isane's attack boost.

Combo skill on main is nice, but it won't happen every round.

Crylix

theunknown404 replied at 2018-12-28 04:42
I would prioritize Isane's attack boost.

Combo skill on main is nice, but it won't happen every rou ...

Still, which of the two skills do you think would be better even if not T1 for main?

theunknown404

Crylix replied at 2018-12-27 22:46
Still, which of the two skills do you think would be better even if not T1 for main?

Combo would be better, especially if Isane overrides that 15% attack buff from main.

Crylix

theunknown404 replied at 2018-12-28 04:49
Combo would be better, especially if Isane overrides that 15% attack buff from main.

That makes sense. To be honest it didn't even cross my mind that they might not stack. Plus now that I'm thinking about it an extra attack of millions hp is definitely better than 15% of extra attack added to the normal attack. I just imagined it in my head like this: Attack + bonus attack > (Attack+((attack/100)x15))) (yeah I'm not a math person).

Idk sorry, I feel now that it was a stupid question about main's skill.