As most of you should there is an exploit with Arcane Dynamo ([Wizard] Increased damage with Hydra and Archon), but the fun doesn't stop there!
Apparently Arcane Dynamo has a grace period of a few hundred milliseconds where damage from your hydra can be counted towards stacks... What does this mean? If you get five stacks and cast your hydra then time your signature to hit right before the hydra's attacks land, they will count towards your stacks! (+3 stacks for three projectiles)
Can this get more awesome? YES it can! If you're using venom hydra, and you manage to time your Arcane Dynamo grace period with the poison pool cast, you will get another stack for each mob hit by that tick. The venom pools can also stack so if you manage to time two venom pools properly, you'll seemingly never run out of stacks.
----
I have seen this happening with a number of different spell combos, but I have only extensively tested it with Arcane Missile (Seeker) and Venom Hydra. It can be difficult to time when you are trying to stay alive, but believe me it works.
With the right amount of AP regen and/or reduction talents and some good timing, you can have an almost permanent additional 75% damage on your spells.
----
NO LONGER WORKS