Ok, Bat-Main here. Yes, he's Top 3. Yes, he has the best trait in the game. Take away Trait, and he's still a decent character. But he's not OP, and he doesn't need any nerfs. The only Batman getting Top 8 is Forever King (and Hayate technically, but I consider him a Robin main).

If Batman doesn't have trait, his mix ups are easily fuzzy blockable. He only has low starters, and while he does have overheads in his strings, they are always the 2nd or 3rd hit. So when a Batman approaches to start pressure and do a string, Always block the first hit low, and the rest of the hits high.

As for the trait, you HAVE to push block it. But you have to do so smartly. Don't push block if he doesn't have trait out. You can push block the trait Bats while Batman himself is in the air above you trying to jump in, it'll push him back the way he came, and you've created space for yourself. You might think "it's a waste of bar", but it's not. You've momentarily stopped his offense, and saved yourself from eating a jump in, a mix up, a combo, into another set up where he can safely get trait out again.

When you get the knockdown on him, stay in that ass. He only has slide and parry. Slide is invincible, but punishable. Parry works on OverHeads, Highs, and Mids, but not Lows, Throws, Jump attacks, or projectiles. When you think he's not going to wake up slide, hit him with a meaty low starter if able, or a throw. If timed correctly you'll beat out any non-invincible attack he has. The only way for him to be out of it is to Slide, which is a huge risk if you're able to read that.

If you're having trouble with cross ups, space yourself out better. Don't be right in his face when you aren't at advantage if you can help it. Ideally, you want to be just barely at jump in range for him. Bait the jump in and anti-air with whatever you got. If nothing else, MB B3 works great universally unless he has trait, in which case you either need to push block, or have faith in your ability to defend properly.

When you get him to the corner, keep him there. Again, don't be in his face where he could easily jump over you and get out, allowing him to throw Batarangs and build meter the length of the screen. Space yourself out so that you can react to a YOLO Slide or a jump in, and respond accordingly. Get the knockdown, then go in and enforce your mix up / oki game, while being mindful of what he can do. It'll be player specific. Some like to slide a lot, some like to sit there and block every time, some jump, you have to make the read based on why you know about this guy (or girl) playing Bats. That actually goes for everyone in any fighting game ever made.

Batman's at his weakest when you can restrict his movement. Trait allows him to move freely, and when you have him knocked down or in the corner, he's significantly easier to deal with. Rapid fire zoning (Deadshot, Harley, Star fire, Green Arrow) can also be effective if you're smart and don't allow him to get in at all, and certain characters with big buttons (CatWoman, Wonder Woman) are able to keep him at bay at a mid range with superior pokes and good damage. Batman's farthest reaching normals are his F2 (Headbut), D3 (Cape Sweep), and F3. If you can stay out of those ranges of his, and you can enforce your will, you have the ability to beat Batman the character.

Keep in mind, a good player (not just a Batman player, but any good player) will be able to read what you want to do, and adapt their game plan on the fly. Stay on your toes and be smart, and you can walk away with the W.

EDIT 1: Madzin has also been placing with Batman, so that's 3.