So I see you've attributed the statement that what she does is mentally impossible for normal humans as being mentally impossible for Batman. lol? Batman, and every other active street, operates with the same coordination ability to multi-task without diminishing returns.
Yes, because the reason David Cain trained Cass from birth in the first place was because he couldn't become the perfect fighter and he couldn't train Bruce Wayne to be the perfect fighter either. Only Cassandra met his goal.
The 'mentally impossible' was by a group of people who study metas btw, and know the actual limit of the human mind, scientists. We aren't just talking normal multi-tasking, keep in mind Cassandra has additional areas of her brain devoted to fighting. They said the aggregate speed was superhuman. Not peak human or almost impossible, superhuman and mental impossible.
Batman calls Cassandra's fighting perfect. Bronze Tiger bows to her. These are people who'd know.
Dick said it before RIP and his Batman skill boost. He told her she wasn't psychic, she can only guess what he'll do next, and that eventually she would be wrong and he would have her.
(Ah yes, the Beechen Batgirl mini had that bit).
.... that's not how her powers work 🙂 No surprise Beechen doesn't know that. It's not guessing, it's the opponent's body telling. Dick should know better, Cassandra will never 'guess' wrong.
And, guess what? He tries to stop her in issue 5 of the same series and she brushes him aside with a kick to the face. Also in issue 1, when he says that, she's pretty casually defending against him and disarmed him. Not really the best series to quote.
Heck, the Outsiders one where they fight more evenly, more like he fights when Batman, (til Alfred stops them because Alfred > All Bats) has her shrug a few blows and still was asking him to give up. And yea, he can put up a fight nowadays, but she's still better.
Shiva beats him, and Cass beats Shiva. And Cass is... really, really tough for her size, with defense as her best area. One mistake is not a win, even if Dick connected he'd still lose. Shiva landed many blows on her and still lost.
Batgirl is able to beat Shiva the same reason that most of the time David Cain lets her walk all over his face without fighting back. CIS. It's some twisted maternal / paternal instinct, not any edge that Cassandra has.
Please, Shiva wanted someone worthy enough to kill her and later talks about how incredibly proud she is that Cassandra beat her. Heck, in the Destruction Daughter's story line she talked about how her first defeat against Cass realize her flaws and made her push even harder. Shiva treated it as a legit win and is far less parental than Cain, she cares about Cass because Cass is the one who can beat her.
You're calling CIS but have nothing to back it up, just "oh, Dick held his own once instead of being rolled over," "every one of the people who talk about her performance as if it's the best, which it visibly is, must be wrong or biased," and that sort of thing.
Cassandra consistently does this well and tons of top martial artist back up how strong she is (BT, Batman, Shiva, Canary, Connor...).