Only tried Heroic last night; no idea if this affects LFR/N/M (if the timer is different in other difficulties), but the timer for the first spawn would usually be timed for around when the lovers were Longing for one another (which is well after the first one died and a bit before the second spawned).

Version is the most updated via Twitch: v153. Updated just before raid. Checked after raid and this morning, no new updates.

Hulk timers (and all other adds) will need some more work as there are no spell events.
No ETA on when this will be added yet.

I've been working on weakauras that base off her speech patterns. The hulk comes out about ~8 seconds after she says "Queen Azshara yells: There is no power I cannot defile!."

The hulk does emotes to rush a ward, but not until a second or so after he has become attackable.

21:53:31.595 Queen Azshara yells: There is no power I cannot defile!
21:53:31.595 Drains one of the Ancient Wards!
21:53:40.988 Overzealous Hulk rushes toward an Ancient Ward!

It needs more fine tuning for the EXACT timing, but I've found it's a good estimate for now.

Edit* This is only for the first Hulk and I have only tested this on Heroic.