Dendrobium is now OP yes. The best turn 1 girl.
Cardamine is OP too. Good on the offense side with all her self buff and awesome on support side with her 3 negate damages for herself, guts and x2 skill act when attacked.

For girls who are not on R-medal shop/free 6* ticket list, Konagi and Convoluvus are top S-tier. They are kind of non-crit RRose. Crit is now nerfed. Recentrly we got crazy bosses with Crit rate debuff ability, making all crit teams at 5* teams level.

Tampala is good but I won't say broken. She has a lot of trouble with high def enemies. She needs a lot of Def buff for her counter or a lot of Atk buff for her skill and HP drain. And she is not on the R-medal shop/free 6* ticket list.

Tarragon is a nice Crit+Counter too. Seconded by Firethorn as RG 5*.

Balsam, Prison Island Yarrow and Meconopsis are RRose level and crazy beatsticks. But they are all Crit. Beware the Crit debuff wave above our heads.

Japanese Anemone (Aspirational Relaxed Queen) is very good too with x2 skill act and +30% damages when attacked. Flame Lily is her discount version but not available with R-medals (anyway, everything after Cardamine is not on R-medal shop).

Pursuit is now better. Most girls deals now 30% of total power damages instead of 20% (and some did up too 40%). And it seems it's not affected by defense. As 6* pursuit girls I like Liverwort, Duranta and Hyacinth.
Atk down debuff is nice too. At least, it was needed for some crazy stuff (but it was just a test for the future bunch of hardest stages and it's now gone until the true release).
Solar Blast is very good too with Flower Memories. You can easily get 4* memories that gives +10% Solar Blast damages. Since SB damages works multiplicatively and not additively, it's broken.

Since we are in the middle (or only begening?) of 6* and RG5* rework, it may be a good idea to keep one or two 6* tickets to pick a girl if she became broken.
Oh and maybe you noticed it but they do rework gacha where you can get a free ticket for 55 rolls (=250FG) to choose one of the currently reworked 5* or 6*.