Do not stop building Valkyr. She really isn't that great of a warframe, but concerning your second question, Valkyr is probably the most fun to play along side with Rhino. This is mostly because of her "Rip Line", but "Hysteria" is also a lot of fun.
And Rhino, well he just charges into things.
i started to build Hydroid, i want these water tentacul and that puddle haha. only wrong point with him is he's ugly like fuck :s.
also i'm in the nova master race too (mine is pink #yolo)
hanzo,is there a stance you search, i got some and idk with what it fit.
You forgot to mention that unless people wait around to hide behind you or you've blew a stack of mod points on speed + a helmet 99% of everything's dead before the slow fucker gets to it.
Rhino
Not really o: A max rush mod doesn't really use up too much mod space. (plus having an maxed aura helps a lot)
Plus the helmet is just a speed bonus which isn't hard to get.
So ehhhh, I didn't forget it, it's just not enough of a bother to complain about it xD