Yeah, I haven't completed my pass on monocolored yet. There's the fight dragon in green, and maybe Keiga in blue that I could add, and then maybe the 4/4 for 2RR that burns opponent when a dragon is targeted
I'm a big fan of Thunderbreak Regent, although it would probably be your second best red 4 in a way which is not favorable towards the bottom two. I like it as a burn finisher a lot though. Keiga seems like she could be very annoying. I'm a bigger fan of Icefall Regent for my blue dragon, since it's not too big but still works as a finisher, while being able to stonewall an annoying threat. Foe-Razer Regent is very good, although I don't think it's necessary for Sarkhan Unbroken.