There's still 8-9 months before we get Anniversary update, though. Not to mention that in order to get the set bonus, you need to unlock all five slots, yes? And then there's a hefty (real) Ragnarok Disaster grind per element per character to work on as well.

Shit, that fucking slot bonus is 15% Dbl and 15% Trpl? Yeah, I can see why that's broken as fuck. However, since even Tiara Rs with garbage on them will give you the set bonus, you can just add two R garbage per Hime once you unlock the slots. And there, you have the most important thing done. So there's no particular need to gear for that right now then, just keep in mind that Tiaras are über alles.