I am experiencing very poor performance from Addons utilizing Otravi Unit Frames since the Tides of Vengeance 8.1 patch. I initially thought it was an Elvui specific bug, but it turns out it might be located in Otravi Unit Frames or perhaps even Blizzard's API.
Problem: Whenever I enter combat in raids, my FPS absolutely tanks to 1-20 FPS. This happens with only Elvui enabled with default settings, and all other addons disabled. This also happens with Vuhdo only enabled, another oUF addon.
What I tried to fix the issue: I have tried completely reinstalling World of Warcraft, installing only Elvui or Vuhdo and leaving everything to the default settings, but the issue remains. Disabling the addon and my FPS is fine (50-60+ depending on fight).
Important observations: Profiling shows that some event calls go crazy high with the addons enabled versus disabled. The biggest offender seems to be UNIT_HEALTH by a very large margin, but there are also an unusually high number of calls to UNIT_POWER_UPDATE, UNIT_ABSORB_AMOUNT_CHANGED and UNIT_HEAL_PREDICTION.
Would you mind trying out my layout (comes with oUF embedded) instead of VuhDo/ElvUI? Some layout/compilation creators tend to do odd things to circumvent certain parts of oUF, of which we are aware of are very bad for performance.
Also, are you showing nameplates with oUF during these drops?
As for possible API issues from Blizzard's end, we are aware of some issues in regards of performance with health events, thus we can't control it.