In this case
Desiderius is correct. This is a game that revolves around stacking buff spells and you've basically just got bless, haste, and enlarge person working in your favor? You don't even appear to be buffing Seelah's Charisma for a better smite. I can't see your full party but Arue can use Ranger's Bond to share +4 AB/Damage with the rest of the party (assuming you focused her on a specific demon type, instant enemy can spread it to all others) and Sosiel should have some busted domain power from impossible domain, like Guarded Hearth which will give everyone something like +6-10 AB by sharing his wisdom bonus as an AB bonus. Nenio should have Greater Heroism (+4 morale AB) and rage (+2 morale Strength). Seelah can have Burst of Glory (+1 sacred AB), Eaglesoul (+4 Sacred str, you might have this already not sure), and Divine Favor (+3 luck AB)
For dispelling you use this:
If you're OK with a bit of cheese you can use it, rest, use it on another character, repeat until everyone has their next dispel attempt maximized.
Altogether that's around a 30 to 35 AB swing in your favor if you removed his two AC buffs and had all these AB buffs, and you only need 22 to hit him on everything but a 1 so you can be missing a lot of these and still do fine. And I can't even see the rest of your party to see what they might add.