Change log for v6.80
EMP burn increased from 100->400 to 100->550
EMP delay from 3.7->2 to 2.6

At level 15 with decent farm, your spells can do this:
1100 AoE Mana Drain
550 AoE Pure Damage
680 AoE Damage from Tornado
2.0 Sec AoE Pushback
2.8 Sec AoE Lift
AoE Disarm
Monstrous Mana Recovery!

Situational Build: Only good for Team Battles and Defending Towers
Warning: Do not attempt this build against Split Pushers or Pugna

Instructions for Initiation:

Invoke Tornado first, then invoke Deafening Blast
Tornado, Invoke EMP ASAP, Cast EMP
Cast Deafening Blast
Use Refresher Orb
Cast Deafening Blast
Invoke tornado
Tornado, then EMP

For my comprehensive Invoker guide after 6000+ games, see:
http://steamcommunity.com/sharedfiles/filedetails/?id=185528211#158566