Yeah it was removed since it made mobfarms too easy. We have other options:
-corporeal attractor
-siren's lure
-attraction obelisk
I'm personally using siren's lure. Well I was, since my mobfarm hasn't been running for over a month - I don't need it anymore
Also cursed earth isn't the only way to spawn mobs. There's this TT thing (tablet or sth), Automagy Dimensional Lure, Powered Spawners, bees, and probably more which I don't know of.
P.S. Neutronium ore... DD
I'll probably use the Siren's lure also as it seems the most interesting. Plus, I think if I put it directly under my diamond spikes the mobs will just jump into the spikes, even if they're something like blazes that can fly.
I know cursed earth isn't the only way to spawn things. I'm collecting souls for the Tablet of Necromancy now and I'll use that for some specific things but I don't think it spawns as fast as cursed earth either. Also, I believe I can get pechs to spawn on cursed earth by growing a silverywood pure node there first.
I'll eventually check out the dimensional lure because it's cool and lets you select what spawns. Powered spawners are great, but I don't really have the EU/t for them right now, but I'm saving some space in my mob spawn tower for them for sure. It's also possible to just move a spawner with Thaumcraft.