I think you're the one who doesn't understand how enmity works. Provoke will match the enmity of whoever is highest on the enmity list; thus, provoke > shield lob will always pull the mob off whomever, assuming that the person with highest enmity does not continue accruing enmity.
Furthermore, I think you're using a very odd strategy for garuda extreme. There's really no reason to pull suparna off the MT at any point in the fight. It's also much easier just to leave chirada alive and kill suparna first these days.