Concerning DRK, you need to learn the timing of a raid to see where you can and can't use plunge. Yes, this is going to result in a lost plunge or so, but it's far better to lose a plunge cast than it is to lose several GCDs of uptime.

In cases like omega M/F, it means having an un-optimized plunge, but you do at least gain an extra use for the knockback so it's not so bad.