The Meaning of Life, the Universe, and Everything.
I am too also experiencing significant FPS drops when going near these under water dungeons. I like them alot, but they definitely need more loot considering the ratio of the gold blocks in the center compared to all the Guardians, plus the two Guardian Elders.
It'd be cool if the guardians over time aged into Guardian Elders as well.
In case anyone is wondering what the new block recipes are (Dark Prismarine doesn't seem to be on the wiki as I write this):
Balancing issue: If Prismarine is made from 4 shards, and the recipe for dark calls for 8 shards and dye, then that should yeild 2 blocks of dark prismarine, not just one.
Better: Since we have the brick form of the regular prismarine, why not a brick form of the dark as well?
In that case, 8 + dye should give dark bricks (just as 9 of the shards gives normal bricks), and 4 + dye should give normal dark.
Best: 4 prismarine blocks -- either light or dark -- give 4 prismarine brick (light/dark), just like the other stone to brick forms. Then, 9 of a kind can become a storage block. Dark form can either be 4 shards plus dye, or block plus dye.