I actually think that the inmunities are really good but at the same time they are not unbalanced since you need to waste lot of skillspoints on it and knockdown its a way off CC through phyisical armor, you can still CC him a lot and dmg it with magic and magic CC. I would reconsider the telep inmunity, and i forgot to put the earth resist there.
With the "School path" i was meaning that you can do a "full hybrid" with 2 schools, for example doing a rouge trying to reach the 10 air, so he can move more or a tank with earth to get more armor and inmunity and both at the same time have lot of spells to use.
I said this cose in DOS (at least for my gameplays) i never had a "solid" char, since all of them combine almost all the schools, having mage, tanks, ranger and rogues with adrenaline, teleport, stuns, charm, slow(less ap) and lot more cc and buff (like haste of rogue, really op), and i know that larian dont want to "put an only path to the chars" but i think this is why at least for me the game turns so easy, cose you can make all hybrid chars combining all the 1st school buffs and pros, making a really difference between you and the mobs. Here they put memory slots, its a huge pro to stop this full hybrid builds (since now you dont have to reach the stat to get 100% chance, you have to also have the memory slot to use it) but i want to see the final version to ensure that.