They should have designed BLU in a way that you can't even level up until you learn your spells or you level up by learning your spells or something like that. That way you couldn't enter dungeons and raids without spells like they're worried about.
As for some spells being too strong, like Level 5 Death. They should just make bosses immune to that just like almost all are immune to silence, stun and sleep. Then you wouldn't have it equipped from your spell list.
Just my 2 cents. Thanks for reading.