[Gadgeteer Tom]

It is quite helpful to have Magic Nectar, stamina boost item(s) for bard and gadgeteer, and good weapons (tripleshot crossbow with lightning bolts is handy) - and I've never tried it without having at least two in my party able to summon elementals, then buff the elementals with element shield, haste, enchant blade, etc.
And Turncoat for any elementals that THEY summon is extra fun too (Banish can hit an elemental where it hurts too). Even so, it'll be a long fight - know who needs to be silenced, and try to paralyse whoever the elementals go after to help them too...Eye for an Eye can be quite effective also.