Stymie has and always will be horrible as an SP ability. It's effect is that of a normal ability, and can only be used once. Even if enfeebling magic was the best thing ever, Stymie would still provide very little utility.

The problem with Stymie is there's no middle ground to it. It's straightforward, and simple... it makes you land an enfeeble. That's it. There's no experimentation in that, at all.

SE knows Stymie is bad, I know they do. But honestly Enfeebles as a whole is bad as well. I'm of the opinion that SE should just give up on making RDM so Enfeeble-focused. They've tried for years and it just hasn't worked out.