Tying utility to the cards makes things really difficult because of the RNG.
I think that just depends how you look at it. If you're trying to get a specific effect for a specific mechanic then yeah but there are other abilities for that, cards just make everyone's lives a little better. Tanks, BLMs or DRGs are always gonna get hit by something so just throwing bonus dmg reduction on them never hurts, casters could always use a little more mobility, etc. If rng is going to be a core aspect of them you don't want them to be super important.

Adjust other card effects to be competitive enough to DPS without being a direct DPS buff (Essentially impossible unless other cards contribute to DPS...
There's an idea, could have all the different kinds of utility with a dmg buff added to them. At least then they'd never feel useless.