I'm with folks that Synapse, Citadel and Numina need a rework. Not thrilled with Mantis either but that could be fixed just by making the old men's follow mechanics better or making them assemble eligible and maybe making the requirements on the end more clear (as far as I can tell only the larger turrets count toward spawning Duray?). Virgil, Renault, Manticore, all the trees and newly fun respecs (after the gaps were removed, thanks so much!) and even Mistral (though I could do without the first mission being kill all since the map can be a jerk) are fine as they are. The newer stuff like Yin, Posi 1& 2 and Morty Kal are much more fun. The shard ones are terrible too but I'm not entirely sure they're worth revamping since the zones themselves are also a pain.
Most of all I'd like a new high level co-op or 6. But please, for our sanity, no more long cutscenes or yammering dialogue breaks (looking at you apex). They're great the first few times but some of us are running these things dozens or even hundreds of times.