Its your playstyle
but I still think that magic blast is crap for pure mage(15 seconds of cooldown and only one target)
for 15 seconds I will do 5x more damage with magic missiles
you know 1 second of cooldown is more useful than 15 seconds
but If you are willing to fight 1 enemy every 15 seconds.....you style

.....
I am hardcore player who can stand against whole army
and why to bother to max magic blast if you still use magic missiles to fill time