the tempest spell should be available for all schools, it seems like such a overpowered spell that is not known until later and you cant change schools and then you wont have to start new to try and get tempest, other schools have similar spells but not as OP
(also this is a new account i lost my old account from years ago)
It's op because Storm is the strongest school in terms of damage. Just like ice is a tank school, life is a healer school, death is a solo school, etc. Storm needs spells like Tempest in order to survive during high level boss fights. It's not fair that a school like ice, that already has up to 8000 health with still over 50 resist and 100 damage, could get an x attack spell.
Now I'm not sure if you mean that every school gets their own version of tempest or just a tempest replica, but either way this would be completely unfair and it would make storm less unique and fun.
Yes, Storm is basically the strongest. But their are attribute trade offs. They do not have as much HP's - for example as other schools. They do not have near as much accuracy. so on and so forth.
Every School has it's Strengths and weaknesses, so there is a balance within all school.