Poly tends toward melee characters more than casters... Most of the abilities being strength based. You can go kind of war mage str/int hybrid if you want to make use of these abilities... Or, if you want to go full mage then you can utilize apotheosis and skin graft in the mid game to add to your nuking. Haste from pyro will be a huge help with this path, as free source spells mean little if you have no AP to spend.
I have played with the str/int hybrid poly caster and had fun, but it doesn't feel optimal as my party often highly out damaged me. But, I will say it really came on line when I could apotheosis and get off multiple pyroclastic eruptions. Plus even if you aren't the one ripping all the armor off the target like a focused fighter can, doesn't mean your tentacle smack applying atrophy is less useful
Hope this helps.
