yesterday I downloaded flans mod plus, and have been thoroughly enjoying it, for the first 2 hours; now I find it rather bland. given my lousy internet connection, latency is questionable at all times, and therefore restricts me to single player. I am therefore looking for mods that add mobs for me to fight in my tank, as the vanilla mobs are pushovers.
If you don't mind the set-up, use Custom NPCs. You can set their health, attack damage, pretty much anything to as high as you want, give them AI behaviour; the choice is yours. I play(ed) a lot of single player and I never really install mob mods, so while I may not be too much of a help, I can try give you some advice if you need/want it.
Author Of The 'Hellfire' Series.
Self-Proclaimed Master Of Cynicism.
Lives In UK, Thinks It's Shite.
@Guakstick I have used custom npcs before, but I'm more interested in mods that feature tougher mobs that either spawn in groups like regular mobs at night, or mobs that reside in structures; and more ranged mobs overall.