'Mad Dog' Cain was a tough fight because he could read sorta like her (and happened to be feral), and also she was exhausted from fight after fight by that point.
She does have problem reading non-human body types, until she gets used to them at which point she can handle them as well.
Strong and more endurance, sure, but speed feat wise they're pretty close, Cass might possibly be slightly better, and she has move-reading and he doesn't. Pure skill aside from move reading, they're probably on the same tier.
They have advantages and disadvantages when compared to each other.
There speed feats are close, but Cap's are slightly better.
Move reading or no, she's had trouble with Nightwing, Batman and David Cane in h2h. Her only significant wins are over Shiva, and those are suspect Shiva loses were directly attributed to her having a death wish and secretly wanting Cass to kill her. She isn't as skilled as Cap.
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What's he got that tops her Bullet Dance? (Where she dodges *into*, then out of, the path of four bullets in mid-air, for fun)
Her coordination is also explicitly superhuman. It's mentally impossible to move like she does.
Uh, she's casually brushed aside Nightwing before, I think he's only put up a fight once (and that was really recent, almost immediately before he became Bats), having trouble with Batman is no shame (especially since she seemed to have the edge on those fights, scoring a hit he didn't even notice the first, and keeping him on the run on the second), she beat Ravager who's got superhuman stats and precog, and she stalemates Slade every time they meet. Also, the death wish thing isn't a Cass-specific one, meaning she beat Shiva on the same ground as everyone else. Twice.
I mean, that list is like complaining, "Captain America has trouble with fighters like Crossbone." It's true but it doesn't mean much since Crossbone is really good.