Finisher Moves

Finishing moves seem to be a concept that is well known plot wise, or otherwise, but it never seems to work in game.
If you have a strong move, you use it as soon as possible so you'd wait out the delay and regain enough mana to use it again in leu (sp?) of less 'efficient' spells. mana per damage wise.
It's rarely used as a what it's meant to be, a finishing blow.
It could be a high cost move, be perhaps there could be a more realistic deterrant.
A Finishing move is normally a finishing move because it is meant to finish the opponent off and not allow for a counterattack, and therefore it could allow for after affects, such as vulnerability.

Of course the game isnt really meant to be realistic, but it would be a fun high stakes mod to have ultimates deal up to perhaps 40% (60%?) of life damage, in the average character at the cost of nearly ensuring death or at least counter attack if they screw up or their opponent gets lucky enough to survive or dodge.

I normally dont advocate an active dodge type system, but it would definitely be attractive to some people. I'd prefer, say a hidden potion up the sleave to allow a person to survive and perhaps counter ultimate.