Can confirm in 1.19, 1.19.1 and 1.19.2.
Same. The game turns into a slideshow near a mangrove swamp. In every other biome I'm getting pretty constant 80-100 fps but in mangrove swamps it drops to less than 15, and that's while loading preexisting chunks.
The same issue is present in Jungles and crimson forests as well due to all the vines, but to a lesser extent.
Has anyone found a mod (like debugify) that fixes this issue?
Like previous commenters said this issue breaks gameplay quite a bit, as structures with more than one evoker are now way too dangerous.
This Evoker "alerting" mechanic even seems to work through walls, so getting spotted by just one Evoker is enough for wave after wave of vexes from other Evokers in different parts of the structure.