A few other crazy ideas:
1. ExtraBees has a bee to create coal dust (you can source flint and obsidian from TE, then Compress it. Rather tricky) and a bee to create diamonds (or diamond dust, can't remember which - if it's the latter you'll have to make an Implosion Compressor.) This will take a good few days of constant analysis and breeding, though, but once you've got a purebred line going... (Think hundreds of generations!) Your reward then is figuring out how to automate the hives with pipes, though. On the way, you'll find all sorts of other zany shenanigans and unusual resources. Call it an 'alternate tech tree.'
2. TE in general is a good source of blocks - the Extruder in particular is a fast way to make cobble for essentially nothing, and you can use the magmatic furnace to get lava for obsidian (in principle, anyway - energy cost is a tad steep). If I'm reading these tables correctly, you can convert cobble to diamonds in a ratio of 2^13 -> 1... hmm. That's 8192. On second thought, this isn't a good idea.
3. Have you visited the End yet? Enderpearls have a very favourable conversion of 1 pearl -> 4 iron, which you can then double up for one gold, so one diamond is... 8 pearls? That can't be right... Also probably easier to kill, given proper preparations, and you can save a few for Anchors later. (Remember: they're 3 tall!) Hang on. If you used a soul shard... hmmm....
4. I think I've heard it mentioned that one Twilight Forest mob drops iron picks. There are a variety of ways to reprocess those into iron, which you can then transmute, etc. Probably less finicky than the Endermen.
Oh yeah, and don't forget ordering a turtle to attack the mobs for you. That might also get you the Minium shards, and plenty of XP to boot.