Alright, (I know this is a double post, but would rather do this than edit, since it's a valid addition), I have fixed the problem. I started disabling some of the mods I added to the pack in addition to it's normal ones, and it seems that Lycanite's mobs was causing the problem. Once I disabled it, mob spawning was right back to where it usually is (Is this a good or a bad thing that I just did..?)
Anyways, thanks everyone for trying to help me fix it. Now to go get soul shards...
The thread is solved, I know... This is but a FYI.
Lycanite mobs adds DOOM monsters to the game. It is generally a companion mod to the doomlike dungeons mod, which is a worldgen mod that generates doom-like maze levels/dungeons underground with Vanilla loot chests in overworld and in nether. You're better off without them mobs. They get insanely hard to kill, and with only melee weapons, you're pretty much "toast" early game, and rage quit starts to look like a very good option.
Also, it is a known problem that lycanite's mobs, special mobs mod and Ars Magica 2 hecates do interfere with traditional mob spawning frequencies.
That's all the useful things I have to say on this topic.