but he does start with a summons. the sciroccos and other stuff technical happen after the summons and may be interrupted in rtwp. am knowing most folks seem to think this battle is easier in tb, but is possible to utter emasculate him in rtwp. have done the battle multiple times for azata and aeon routes and thus far he always started with summons and chances are he don't get any other action if you rush him with a strong melee party.
your own summons can be problematic as well as they lead to a potential charlie fox making it less likely your melee will reach and potential interrupt your opponent. sometimes less clutter is an advantage, or at least if you have a strong melee party. this battle is so not like playful darkness who is a melee engine o' destruction. summon a wall o' summons is less beneficial.
you got a ranged and caster heavy party which as already noted is not ideal for this battle. the boss in question has a relative unimpressive ac and cmd. if you surround him with melee combatants who all have outflank and most of whom have ever ready, he should go down quick enough. if you are going court poet am understanding why your party is mostly casters + seelah, but there is nothing wrong with switching things up for this battle. for example, regill has high dex and with levels o' sacred huntsmaster you may stick him on a velociraptor or some other critter.
aside, we did try and do the battle via an old azata save and we got a bug in spite o' no mods-- the boss in question has 3hp. he has 64 ac on core and with all buffs he gots a functional ac o' 72 on unfair, both o' which is zero challenge for our level 19 party, but he nevertheless has only 3hp and his caster level is presumable set at 1, so is kinda a pointless encounter in our game at the moment. will check an earlier azata save later to see if that is also bugged. weird.
edit: fixed the bug
did again on unfair and core and the battle is clear skewed in favor o' a party which is able to deal weapon damage asap. our party were lann (zenn archer/divine hunter with a velociraptor,) regill (got 12 levels o' sacred huntsmaster and a velociraptor,) ember as a fire spammer, sosiel with 1 level o' crossblood sorc to exploit ice spells (no madness domain, rides a boar) seelah with 1 level of sohei, and the main is a skald/crossblood sorc (18/1). no protective luck or fortune exploits. regill with his bane boosted gnome hook hammer and lann's velociraptor were co-mvps although the guarded hearth + mark of justice + skald bonuses were functional what were the winning formula and we would need to serious rethink our approach with a caster party.
raptors has been nerfed considerable but a celestial raptor nevertheless provides significant damage potential for boss battles.
ember died each time we did the fight on unfair but survived on core.
boss ac on unfair with all buffs is actual 91 but that were not a genuine problem.
additional late edit:
if our game saves weren't so temporal remote, we definite would include ulbrig in a party to take on the particular boss in question. greyboar dishes out serious pain, but his precision damage is wasted in this battle and he is so slow, relative speaking. trever is not complete terrible, but he is also slow. we do not use camellia, but for most non ranged builds she is crit driven, although if you give her the metal curse her usefulness increases significant. arueshalae is ranged but her instant enemy + hunter's bond is gonna power up your entire party so she is a good choice in our opinion. even so, am thinking ulbrig and regill is obvious choices.
HA! Good Fun!