Some stuff people have deduced from the extreme primal trailers (all guesswork and speculations obviously):

Ifrit:
- Eruptions can't be stunned (was obvious that was going to happen though)
- Summons 8 nails at some point, 7 around the outer edge and 1 huge one the middle.
- Safe area of plumes isn't always under Ifrit, it moves around the arena so tank will have to move him around a fair bit and learn where they appear.
- Does 4 dashes, sometimes simultaneously (could be like 1.0 and you have to break his horns or w/e to stop this).

Garuda (Video was pretty short for this one):
- Tornado patterns are different.
- Uses Aerial Blast every more than once (maybe).
- Sisters aren't one green and one red, can be both green or both red giving either huge regen or huge damage boost.

Titan:
- Uses Geocrush throughout the fight so the arena over time becomes absolutely tiny, by the later stages it's just the orange patch in the middle. Guessing if you take too long it just becomes impossible.
- Tumullt also has knockback, so you have to keep running towards the centre when it's going off.
- He jails 2 people at once, but you have to use the jail to block a new stomp type move or you get knocked off.
- Landslide goes in 4 directions at once, 1 directed at the tank and then a 3-way spread towards other party members.
- He summons Titan-Egis and they use enkindle to do AoE damage and Razed Earth (big patch of crap that stays there for a long time).

Best Thing:
You can queue for these using the duty finder. GOOD LUCK WITH THAT!