Probably the difficulty of punishing blocked lift when used at max distance, air Oa's, the fact that The B1 Strings of Scrub Doom can be thrown out at any time due to their speed and safeness, which means you always have to be ready to block low. Which then can open up the overheads. I know what you're thinking: F3 isn't that fast. I'm sure it's about as fast as most standard F3s, and even those are hard to react to.
Really, it's the amount of space you have to respect with Lantern and how he very much discourages all manner of jumping.
But again, Batman does all right with him, so I've no complaints.