I believe people have misunderstood the OP, anyways.

I can't think of any wasted skills. I think for example if you had DRK and MNK then the DRK will not use Delirium since it does not stack with MNKs Dragon Kick. In this case it cosidered a wasted skill.

NIN and WAR have storms eye and WAR is expected to use it.

So it will depend on the party composition.