What steps will reproduce the problem?

1. As the title says
2. People are using TC2 or Details Tiny Threat

What version of ThreatClassic2 are you using? (Stating 'latest' is not useful)

latest and 5-6 of our member had outdated versions of TC2 (maybe 1-2 revisions back)

Do you have an error log of what happened?

No

Any additional information? (example: WoW language if not English) (Attach screenshots here if available, do not link externally)

Other users seem to have the same problem according to this reddit
https://www.reddit.com/r/classicwow/comments/f5nh60/big_frame_drop_during_nefarian_phase_3/

Any idea why this happens or is it maybe caused by Details! tiny threat syncing with TC2 users through LibThreatClassic2?

Blacklisted now Skeletons, Infernals, Totems from Nef Encounter, lets see tomorrow if this will minimize CPU usage. Will commit if this works!

I already opened a PR for the Corrupted Infernals; they definitely cause lag. The Bone Constructs and the Corrupted Totems should be blacklisted as well. Am I missing any totems on this list?

14663 Corrupted Stoneskin Totem
14664 Corrupted Healing Stream Totem
14666 Corrupted Windfury Totem
14667 Corrupted Fire Nova Totem

I already opened a PR for the Corrupted Infernals; they definitely cause lag. The Bone Constructs and the Corrupted Totems should be blacklisted as well. Am I missing any totems on this list?

14663 Corrupted Stoneskin Totem
14664 Corrupted Healing Stream Totem
14666 Corrupted Windfury Totem
14667 Corrupted Fire Nova Totem

Here you go, everything that could cause a lot of Threat Calculations:
[14605] = true, -- Bone Construct
[14668] = true, -- Corrupted Infernal
[14666] = true, -- Corrupted Winfury Totem
[14662] = true, -- Corrupted Fire Nova Totem
[14664] = true, -- Corrupted Healing Stream Totem
[14663] = true, -- Corrupted Stoneskin Totem

Thanks! I added them all to dfherr/LibThreatClassic2#20.

hopefully fixed with v2.12