They didn't remove slimes right? what has happened is that with the advent of dungeons coming back static world mob spawns have been decreased drastically to make lag more stabile. further there are only what, like three?, swamps this map, one in pvp and two in pve, and with mobs being almost non existent from world spawns the number of swamps matters even less. You can run an entire night cycle in some areas and not see a SINGLE mob.
42 alchemists require that they first either make grass blocks with saplings which requires farming trees, or that they use silk touch which at the moment is nigh impossible to get short of a great pick of notch with insane random roll. I had a town alchemist feeding me slime balls for a whopping 2 days before he was just absolutely burned out on the whole process so he respecced to another profession.
I'm not saying slimes should come back in spawner form because they are just so damned easy for anyone with aoe to farm, but what about a pvp dungeon with pvp enabled for them with very very low exp returns. Tuning down their exp would be a nerf to them in the over world, but as people have already stated, you almost never see them now randomly anyway. If we added them as a spawner that gave lowered exp in a contested area, it would encourage pvp there to farm slimeballs which i personally think could be fantastic.