However, I did Zul'Aman yesterday on my feral druid, and it was quite obvious on Nalorakk (bear boss) that successful taunts weren't being detected, as neither my threat nor the paladin tank's threat changed at all when we taunted the boss off each other at each form change.
Hi Phanx, first of all, thanks for the report. As I wrote the recent patches to Growl/Taunt, it's my responsibility to fix this.
However, I'm afraid I'll need a combat log and/or a way to reproduce. Before this change went live, we tested it with random mobs in Terrokar, and I repeated this test last night, it works fine. I haven't done specific tests in a raid setting, but I'm full time Feral and haven't observed anything suspicious.