Slade has been weakened due to being younger. He has 2 eyes instead of 1 which he stated previously threw him off his game. And as you mentioned Harley hit him from behind while Slade had Bruce against the wall.
I really don't get how this is a good showing for batman.....Yes Slade was being "outsmarted and outfought" through out the fight but he is hindered right now and batman needed a ton of context in this fight...And he still needed to be saved by Harley...
Imo this means nothing because in this title since he's been deaged he's still pulling off uber feats and beating people like Bronze Tiger. If he can take down Bronze Tiger with no gear but can't put down Batman its a good showing for Bruce.
He's been complaining about his new eye throwing him off for awhile now but its more along the lines of him not being used to having two eyes. Slade is weaker because he's been deaged? Don't make no sense to me in this very issue he picked up a huge slab of stone and hit Batman and then he survived the explosion.
Deathstroke mentioning his mind not functioning fast enough is Tony Daniel yet again failing to realize this new 52 Deathstroke isn't amped with 100% brain cognition. He even lampooned this fact in issue 1 IIRC
Several writers integrate Batman into the larger DCU and make sure he takes advantage of being in such a large wide universe filled with so much magic and technology.
Lately Batman has been operating under the philosophy that he can handle any situation. fighting vampires no problem,boom tube the bat family out to apocolips to revive his dead son no problem, handle superman's new archenemy no problem, stop a rogue justice league no problem.
No fear, No doubt just into the fray.
DC seems to be hearkening back to those iconic words from the Nolan trilogy. Its interesting even the upcoming movie Batman v Superman promises a Batman more connected to the comics who won't be held back by realistic human constraints which implies he'll be closer to the current Batman can have no limits mindset setting in from the comics.
Batgod is one thing but being truly prepared and ready for everything is something else entirely.