For reference, since no one ever uses or talks about this skill: http://torchlight2armory.com/skill?i=Overload
I'd like to propose a few simple changes to Overload.
1. Remove cooldown
2. Bump up the damage increase per charge, and make it stack independently of Focus/+% Electric Damage/+% Damage
3. Remove the WDPS component
The idea behind these changes is to make Overload's damage highly dependent on gaining charges. It should be extremely weak when cast with no or few charges, and pretty strong when cast with a full charge bar.
The reason behind removing the cooldown is to have it scale with the increased Charge rate affix. A cooldown would only place a hard cap on the amount of Charge rate increase affix one might want to have.
Removing the WDPS component prevents weird spell trigger shenanigans (and would make balancing the spell easier too, I suppose).
This would have better synergy well with Charge gaining spells: Shield Bash, Dynamo Field, Supercharge Weapon, Charge Domination.
Players would also have to manage their charges well between Force Field and Overload.
Fire&Spark also synergises well with Dynamo Field.