I have 15 fps, there are performance mods in my client
Entity Culling, EBE, Sodium, Nvidium and the like and so on
The mod Infinite is very cool !!👍

as of Alpha 1.7.2, I consider it fixed as now the structure spacing is capped at 6 chunks minimum.

hrrm.
i never thought about structures being able to spawn that frequently from the mob perspective.
will probably reduce the maximum possible density of structures in a future update.