This is indeed very strong in defenses. How is the Spell Damage? Its a big loss with the power-level and Might?
If I keep the might in 14-15 with lower dexterity (and a bit of resolve drop) how this affect the tankiness and damage? Do you guys think is worth it?
The spell damage is actually very bad compare to a pure wizard evoker stacking fire power levels, like, you can't even compare the two, meteor shower has ridiculous base damage and scale off both might and int, those type of wizards can probably 1 shot the final boss with empowered meteor shower or concelhaut's crushing doom since boss has low deflection, while this build's ninagauth pillars are only good for killing low level trash, this build was just an attempt of me to try the tanking concept, now that I look back wizard is probably not the best class for this setup, I'm currently working on a soul blade cipher/paladin build next using the same ideas which I think might be better than this build.
As for your next question, I don't think lowering dex is worth it because you lose reflex and a lot of the final boss's attacks targets reflex, dropping resolve is okayish since theres source of deflection like the intimidate chest, but I still don't recommand it since I consider might a dump stat.
In conclusion, if you like casting powerful spells then you are better off playing a pure wizard, this build is sadly very boring when it comes to fighting the tough bosses.