Been wandering around the wilderness for quite a while and have not seen 1 custom mob, did they remove them?
Nope, they're still there. I see a couple enraged mobs every night in the wild. I haven't seen a miniboss in well over 6 months, though. I've been getting unlucky there.
Go to the bottom of any big dig site. (Example : smp1 /waste e) and mob hunt around there for awhile, especially at night; you will find quite a few enraged mobs. I have yet to see any mini bosses yet myself. But combine the fact I'm not out hunting them, and also there currently was a nerf on the amount they spawn; I'm not surprised
Something definitely happened to the spawn rates of momentus and marlix though no one will admit to it
I was out the other night, and ran across an enraged creeper that met the short end of my sword...(mostly) . I find that deserts seem to be an easier 'find' (they cannot hide) and that killing everything you run across at night tends to help me run across them! Good luck!
I have seen 2 Momentus in 1 block deep water, right next to a grassland plain, if that helps. Those are the only mini-bosses I have encountered my entire time on EMC. Hope that helps you out in some way.