There were a lot of spells that were way too situational to deserve a place on the 8 slots.
For example:
-Flashfire
-Mind blast
-Revival
-Lightning bolt
-Wall of ice
-Horror
-Veilstrike
-Disruption field
Not many people actually worked with those spells. Unless for RP reasons or they had nothing better to use.
I think Veilstrike is good, but in general, yes. You can't make your mages as diverse as you should be able to because you'll have to use the most general purpose spells just to be effective. All of the good, but more specialized spells are seldom used 
I have played about 10 PT's, 6 of them being a mage.... never used lightning bolt....
I tried it out last playthrough. It was pretty good (especially for combos), but the mana cost was absurd (seriously, why do this and Winter's Grasp have such high mana costs for only doing a tiny bit of damage and immobilizing an enemy?) Had its own animation though, which looked cool.