You can make a perfectly working hybrid with around 60-70 int. If all you are planning to do magic wise is to use heals, purify, corrupt and the occasional magic reflect. And possibly some mind blasts.
Thursar can definitely hit 60-70 int and some psy to push their mana to around 100.
Is it min max? Hell no. Can you have fun with it and win fights? I don't see why not.
Heck In mo1 I used my thur/kallard fighter as a mage/thief/dagger user hybrid for a long time out of sheer derpness and I was topping the leaderboard on grey kills at the time. Which is not as impressive as it sounds, since not a lot of kills were against greys, so the competition for numbers there was kinda low. But it still means I managed to beat people, just that I did it blue and not as a murderer. Mo2 is a different game however so that is important to put in mind.
Should you min max? Probably. Is it necessary and will it actually mean you win more at all skill levels? No.
I'd rather play a character I enjoy playing and play to its strengths than min/max and hate my character as well as have a vast array of mega weaknesses for the decision to excel at specific things.
Thur/kalls were almost unheard of when I was playing as one, it was the absolute apex of a min max towards damage bonus. And I reaally didn't play it like it and I had fun, and solo or with Aegis imperium. Winning.