I like the idea. SpankWustler is absolutely correct- enfeebles do not matter for trash mobs, trash mobs die in mere moments. RDMs need desperately need new enfeebles (that actually land) to have a seat at the HNM table.

Honestly, I don't think that Sadness would be too broken to use on HNMs if they made the potency based off of dINT instead of the duration. (Like Slow's potency is based off of dMND.) Go from Store TP -10 on the low end to -50 on the high end and it would be useful but not game-breaking. (Besides, it seems like every new monster added anymore has Auto-Regain.)

Pain is a great concept, but to be a plausible spell that they would implement I think that it would be a reduction in the computation of statistical modifiers for TP moves, not a flooring. Maybe go from -25% to -75% depending on dINT. Once more, it will have an effect on HNMs, but it won't be a "press button kill NM" type thing.

Heat sounds nifty, but it would have to be heavily nerfed if it was added to the game. They would probably make NMs would maybe take 10%, HNMs maybe 5% if that making the spell fairly useless.

But really, RDM needs more outside of the box thinking like this in order to be a productive job again.