Earth shock glyph for the win. Combine like this for INSANE burst:

Fire novas
Flameshock + 3x Lava Burst
CL
3x Earth shock
<0.5 second GC or less>
EM + Thunderstorm


(Edit: you could put EM on CL instead or for extra long range punch, there are several combinations for this)


Anyone standing ~12 yards or closer will take, guessing for a lvl 80 team, roughly 40-50k damage over a period of perhaps 1-2 seconds.
Glyph of CL is funny-looking at best. Your 4th CL hit will rarely land, and when it does, it outputs minimal amounts of damage. Go for something more useful for pvp.