The anvil trick was indeed an exploit, and Moze when he created reborn patched that for us, We have no intention of re-introducing that exploit (But we do have plans for the anvil).

I will be blunt, I don't think you read everything that I've wrote.
Changed the original structure to require SS:TOW blocks **(replaced the end stone to make it a little easier)**

You no longer need end stone when we release this update, so that makes it more obtainable early / mid game as once you've gotten the soul forge, you just corrupt a bunch of stone into the raw version of the new blocks we've added and you're good to go, also you can make shards pretty early in game, all you need in a vanilla example is 3 cobblestone, 3 diamonds, 4 sticks, 7 iron and 1 bit of flint and you're in the nether pretty much straight away to get the glowstone, soul sand and the obsidian for the soul forge. If you have Tinker's Construct, you only need one diamond and if you have open blocks, you don't even need the diamonds as the mod has a block smasher a.f.a.i.k. can break obsidian.

The way the mod is currently structured is to give the mod a sense of balance, if you had an item that leveled up your spawner at your base, that would be insanely unbalanced and over powered, which would basically ruin any other spawner mod out there, as well as the fact that most people wait until the soul shard is at least tier 5 (to get the most out of the spawn rates) before using it to power their bases, so to us that's a non-issue.

You do know you can right click (with a shard) onto a mob spawner it'll absorb the spawner and level up your shard faster? (Config options for any spawner not just matching type, and how many "souls" it gives you when it absorbs said spawner)

Yeah, Jabba Dolly's and ExtraUtilities Cursed Earth combined does hurt the idea of mob spawners such as SS:TOW, EnderIO, MFR, DE and any other spawner mod out there, but look at it this way, if we just make a spawner that you craft and place down and it spawns 100 mobs each spawn tick, that would render every other spawner mod out there, let alone servers and players worlds unusable.

Also, iirc, the vile sword didn't level the shards when it wasn't in your inventory, it just allowed the shards to level up faster buy giving extra souls per kill (which is what the Soul Stealer enchantment does)