The powercreep has gone too far. Even new regular rainbows struggle to be meta. The top tier is mainly occupied by limited gacha 6* (aka girls you can only get in their special gachas for a short time then wait until they come back at dev will). The old top tier are not viable anymore sadly.
There is almost no new gacha 5* (last one was on event 220). Only event 5*.
Event 5* Poison Berry is excellent. Top tier Slash ally support. I think we are 3 reprint away from her. Must have with top tier like Bunny Cactus and Niddhog (girl, not boss) around.
I really like Winged Everlasting too but her reprint was last week and ended already.
I don't even know if they still do rereprint...

I guess that's almost all. But now, you can farm Rainbow shards for RG every 7 and 27 of each month. There is a really easy nazuna-stage available for the whole day where you can get 1~10 shards. That's cool.