We did, though, even though it wasn't a whole lot.
After Slade awoke on the ship and rushed back to Ollie, Shado, and Sara, it was clear he was superhuman. His blows were making guys fly across the forest and he snapped a rifle in half with his bare hands. We also know that his blood was what gave Cyrus Gold his own enhanced powers...something that Ollie specifically referenced as being familiar with.
I would take Island Era Slade for the healthy majority against Bale's Batman as of right now. Once the series returns, that gap is probably only going to widen.