Do Poppytail and Darkflower have a rivalry brewing in ShadowClan? For that matter, how does Burnetdusk feel about Blackfoot? It looks like ShadowClan expects perfection from more cats than just their Seers.
Poppytail and Darkflower get along fine! Some question how the -flower cat didn't become matriarch, but Darkflower's simply more interested in raising her own kits before taking care of everyone else's (and the everyone else included), and Poppytail likes guarding the nursery and keeping track of family lines.
As for Blackfoot, he was chosen by Brokenstar because he's quiet muscle who didn't question Brokenstar's decisions, just enforced them. For how that whole situation is resolved, did you know that burnet is great for gastrointestinal problems such as dysentery and enterocolitis? The huge amount of tannin in it helps clot both skin and the mucosa, so it's also a good blood-stopper.
For your last comment, ShadowClan values perfection, but moreso they value dedication. You don't have to be perfect if you're throwing everything you have into doing your best and sticking with what you care about. A -tail fiercely protecting the nursery is going to be more highly praised than a -flower who just likes playing with kits and doesn't do much beyond that. Having something you love and wholeheartedly devoting yourself to it, whether it be a religious role, a task, or knowledge on stories, is very important to ShadowClan, and something they believe is part of what it means to be a warrior.