RDM was never that big a deal for enfeebling.
NIN had two-tier enfeebles before we ever even got introduced to merits, and BRD Elegy has traditionally outshined Slow with minimal effort, in addition to Lullaby which picks up where Sleep falls down. BLM and DRK make better use of Bio simply for having higher Dark Magic skill and wider access to Dark skill equipment. Let's not forget that BLM has always exclusively held the elemental DoTs in Choke/Frost/Burn/Drown/Shock/Rasp, any three of which bearing similar affinity can be staked, any two of which bearing neutral affinity being stackable, and has native Sleepga access. We have to sub DRK or BLM for Stun, PLD for Flash, and since then, WHM has gained native access to light-based Repose, which was, until the cap raise, exclusive to WHM. Meanwhile, BLU gets access to Disease in Lowing, regardless of whether they actually use it. RDM never so much as narrowed the market on unique spells, let along potent ones.
The only reason people jock-ride RDM enfeebling so hard is because they were eager to find something to attach the class to and got gassed up by it's status as our only A-rated skill, a status which has been of ambiguous benefit since about the release of ToAU.