Not sure at wich point he starts to use those, but it's most certainly one of the instance "triggers", like the Stephan mechanics.
From the ones we have on iRO so far, it looks like MVPs get stuck into completing one trigger mechanic before moving to the next one, so high dps at certain phases may skip them?
Need to confirm that, i only have vague memories of doing sky fortress and having the EQ spawns a bit slower because i'd start bursting him when it announced the prior mechanic. It gave me like a 15ish seconds leeway until EQs would appear.
Tried to solo NOGH on my RK, can't be done without a GTB shield haha. H Amdarais spams too many highly damaging spells at 20% HP remaining; it's like someone took Bakonawa mechanics and said "I'll just add a 0 or two to this number anddddddddddddddddd good".