It is not even 50%, it base health excluding all HP gained from the lock and talents and buffs of any kind. So 3K hp in case of FG, less in case of other pets.
I’ve played a tank through this entire phase. And learned early that i need to always put the imp in phaseshift in any boss fight or it may get killed during the fight. This i pretty annoying. Also if i get kocked in the lava at Ragnaros, even when the pet is in phaseshift it takes dmg and dies from the lava. So i also had to start putting the pet on stay near the boss just in case i get knocked.
Why not play with FG as a tank at that point (does not have problems with dying and can keep dealing damage)? Incinerate? UA?
Keep in mind that zg trinket and bwl trinket (black book) share the same cd.
Wait what is the shared CD in SOD? I thought it was 15 sec for some reason (and some trinkets I have right now have no shared CD at all so I am not sure how exactly does it work).