It turns out the OnUpdate code was unnecessary. Lifebloom doesn't update often enough when you just have your own buffs, but CompactUnitFrame_UtilSetBuff fires very often under normal use case, resulting in desired accuracy.
https://www.wowinterface.com/downloa...bloomGlow.html
For anyone following the thread or people coming from google, here is the addon if you don't want to worry about what to do with code or whatever.
Cheers
