I feel like the mystics don't lack diversity, which means pretty much every one of them has a different use. BWCV is better because she can do things that other mystics can do, for instance she can regen and power control. Her main thing though are her immunities and how she works with them. Dr Voodoo is still my favourite, but BWCV is undeniably better. Not sure if she's better than Sym Supreme though...
I mostly say this because DV has been around for far longer. If you already have a ranked up Voodoo, I personally don’t think Claire offers much more that would justify using resources on other than if you desperately need her immunities. Voodoo has regen, power control, buff control, better DoT, and ability accuracy reduction. I was struggling to find a reason to bring Claire to R4 when I already have DV at R5.