More testing on Glass Cannon
I decided to swap my lightning spell lines for fire, to see what would happen to the damage output of the Glass Cannon. So that puts me at 7/6/6 force and 7/2/2 fire - it about doubled my damaged output. Now I get between 300-1600 damage per mob, depending on how they save. Evasion can make that number a 0.
So the force line is doing 150-800, with the fire line comparable, but perhaps a bit less (they seem close enough to equal that I haven't noticed much difference).
Otherwise, with the rune arm on, I have 225 kinetic and 195 fire.