It arguably didn't pick up until you started seeing NIN/DRKs floating around, who in part shared some of RDM's hate-gaining tools. If RDMs didn't pick up on this and add things like their -interrupt sets, innate stoneskin/phalanx, and an easier time of capping recasts, it's possible the nerf may have never happened since the NIN/DRKs were at least reliant on an outside source of Refresh, and thus more vulnerable to things that could mess with your MP.

In general, I'm not against the concept of RDM tanking, I'd just like it to be done right. Exploit, loophole, oversight, whatever you wanna call it, the "No Effect" might not have been bad, but it wasn't good game design, either. Instead, consider what would make RDM a unique tank, as for now, we're basically and always have been a pseudo-PLD in this regard.