Illidan threat reset problem with field material!

[Alpiino]

So, Illidan resets his threat when he switches from demon to normal.
The following happened this evening when Illidan transformed from demon to normal form:

21:21'41.500 Celendir's Insect Swarm dots Illidan Stormrage for 313 Nature damage
21:21'42.593 Alpiino's Swing hits Illidan Stormrage for 180 Physical damage
21:21'43.109 Celendir's Moonfire dots Illidan Stormrage for 454 Arcane damage
21:21'44.015 Alpiino's Shield Slam hits Illidan Stormrage for 477 Physical damage
21:21'45.765 Illidan Stormrage's Swing hits Celendir for 12312 Physical damage

That is all the threat relevant action done by me and Celendir between 21:21'41.500 and 21:21'45.765 when the poor druid died.

So the question is when does illidan reset his threat and start receiving new threat? When he begins the transformation animation (lies on the ground and shakes)? I have tried to time my shieldslam based on Deadly bossmods timer. When the timer of normal form hits 0 I shieldslam him.

WWS parses that I took the information from:
Wow Web Stats (http://wowwebstats.com/1b1cidu5vrgte?bl=9508)
Wow Web Stats (http://wowwebstats.com/1b1cidu5vrgte?bl=9514)

And full WWS of the fight: Wow Web Stats (http://wowwebstats.com/1b1cidu5vrgte?m&s=8882-9833)
As a side note, we killed Illidan at that try and got our first legendary offhand ;)

EDIT: I did a bit of additional research and everything points out that he resets aggro right after the last fire AOE when he starts the transformation animation. Can anyone confirm this? This would mean that threat should be built and MD:s should be shot when he is lying on the ground.

[Worldie]

I'm quite sure that the threat reset happens when he "changes form".

However, noone should be dpsing at all since when demons spawn.

[Stroja]

We normally have DPS stop during transitions. I generally run up and start auto-attack and Consecration while he's on the ground, and Judge as soon as the Target-of-Target frame comes up. The only person that should have any threat besides me is our demon-phase warlock tank who might not get all his DoTs cleared - and we have a holy pally ready to BoP him if Illidan decides he looks tasty.

Waiting until that ToT frame seems to be the winning key for me - but I've got a 10 yard Judge and a 30 yard Exorcism to spank him with if he turns chicken and tries to run away.

[Lokdar]

I'm pretty sure the reset happens when he's in the transition phase of turning into a demon or humanoid form. During demon phase after the last flame burst, a few seconds later, he'll be on the ground. Like Stroja says, this is when you should be auto attacking, shield slaming etc. When he comes to, you should always have aggro this way.

[Alpiino]

Confirmed this. He resets when the animation begins.

[Jock]

Every report I have seen says that the threat drop is before the physical switch (demon to elf or vice versa) meaning that as soon as he falls, the threat drop takes place. Note that you can still get the effect of the aura if you get in too soon, but the only shadow dmg you take as a tank is drain soul and parasites, so this shouldn't be too bad. Try getting in right after if it is possible. This will leave you plenty of time to unload a full rage bar and have threat (provided the dps stops at the transition).

[Worldie]

The aura actually lasts just a few seconds, so it will end by the time he stats autoattacking anyway.