From what I've tested, GL gets a free dash after pretty much any projectile, except for Cyborg's instant air bull and just a few frame traps.
Deathstroke has one frame trap, that works on GL where he can do low shots into high shots. It has to be right on top of the other in order for it to catch you, though. Either way, you still get a dash in and lose little ground as opposed to jumping right into it and losing ground.
Batman has a trap where he can do a full screen batarang and then catch you on a dash with his grapple. With that in mind, just jump forward after the bats and duck (keeping in mind the range on his up grapple and air to airs). Gain ground and safe.
Raven has a trap where she throws out her df1 and then can get you with her df2 or her db2 if you're in range if you dashed in between. It can even be hard to dash in between her df2 if she's just throwing it out there a lot, but the chip is so weak that you can just walk and crouch and not even worry about getting that dash in. Before you know it, you're right in that sweet spot and can punish her.
Ares has some tight projectiles, but I can't seem to find any combination that is impossible to get a dash in on. I personally have a lot trouble against that character, but that's just in regards to his up close game (he's safe on everything!). For the most part, you can dash in after blocking anything and be safe. You can also punish quite a few things from what I've found. You won't be able to punish the axe throw if it hit you twice though.
Cyborg is broke. I mean if you're going against one that isn't abusing his instant air nova blasts, you still won't be able to dash in between grounded novas. You can still jump them or walk and block them. But since most Cyborgs are abusing the block infinite (even trying it is still enough to just cause problems for everyone) there's nothing much to do. Bonus! If you're somehow get in on a Cyborg, there's a slim chance you can LM him out of his grapple. The very frame he is airborne, he can be nailed. Not sure if that was known tech or not, but just thought I'd share it.
I don't know. I really don't feel like GL gets zoned that bad. He definitely doesn't have as good or clear of answers as some characters, but it's definitely not that bad. 2 free dashes in from pretty much any projectile and you're in. 6%-12% chip, that you may not even get because you can duck a lot of projectiles, isn't as bad as some people make it seem. I'm not an expert at this game by any means and these are just my thoughts and findings. Hope they contribute sort of :/
edit: I tested Sinestro. Why does he zone out GL? I can't find a thing he can do after a blocked special unless that turret is out.
