So back in the day, prismatic spray used to do 50-150 damage when people had max hits of 180-550 and the most elite characters double massacred and cyan only had 2k hp.
Nowadays it does about same amount of damage except people have 350-1000 hp.. on top of that for zoning you need elite dps classes to do high sustained damage every round for long long fights. Using mages best spells they cant keep up with the dps of other classes even when they are memmed and then when they cast all their spells, however after like 15-20 rounds they are completely worthless, and then they have to mem.
My only two ideas so far of any note are these:
1) increase spell dam so it can be on par with high end dps of other classes... I mean mages need 30 cl of gear, other dps need +dams... both need gear I dont see why mages who have 30 cl still do 0 damage.
2) Possibly change it from a spell mem system to a mana system that constantly replenishes. So for example, start with 1000 mana, but a 9th circle slot costs 200 mana, a first circle slot costs 10 mana, but at baseline you regen 25 mana per tic or something, with extra gear increasing mana regen?