Have you already clicked all of Torchlight 2's many monsters into a fine paste of gibbed chunks? Then the Synergies mod could be exactly what you're looking for. It's a huge overhaul of the game, billed as a "Full Conversion" that adds in a number of new Elite-class mobs, extra maps and bosses, and an entirely new class. Amazingly, this is all without the still unreleased GUTS game editor.
The new class, the Necromancer, is a nice balance of Embermage style magic attacks, the Outlander's holds and status effects, and a ridiculous number of summoned monsters. The primary skill, Skull Barrage, is brilliant: a multiple projectile attack that, at maximum level, lays down exploding pustules of poisonous goo.
Elite mobs provide a bigger challenge throughout the campaign. Really, though, the mod is geared toward the end game, adding in "raid like dungeon chains", new world bosses, overworld maps and armour sets. While there's nothing new visually - mostly thanks to the absence of Runic's official mod tools - there have still been enough changes made to give Synergies a different flavour to the vanilla game.
Synergies is available to download from the official website , and comes packaged with a number of other community mods. Here's a video of the Necromancer in action: