I selected the disagree tag, not dislike.
If charisma was used then classes like Bard would be flat out stupid, and classes like Dreadknight wouldn't have any other benefit from it.
I don't agree with adding a new attribute. Not only would this create more pressure on the balance team, it would probably mean more coding than you think. Attributes (from what I can tell) are hard coded, and so Heroes itself would need changes made. Then there's the transition over from how cool-downs work now. You'd need to change skills configuration to not only read from the file, but then determine what the actual cooldown is. Then, it's possible some skills would need their cool downs changed to not get broken. Some skills currently have very short CD's, having this attribute could cause them to be far too spammable. Attributes per level may need changed, wiki would need changed. Adding a new attribute can imply a lot more work than you'd first think.