So I was wrong - the new combiners only need 5 units each. Very happy I'm wrong though
Optimus Prime, Sunstreaker, Mirage, Prowl and Ironhide for Optimus Maximus.
Onslaught, Swindle, Brawl, Vortex and Blast Off for Bruticus.
Sorry for the terrible pictures
They both have less power but more health than Superion and Devastator. They also have the same abilities as each other; a shockwave that does 6X damage to walls, a stat buff and an ability that sends 4 missiles that deal massive damage to and disable 4 defences.
Anyone else think Optimus Maximus looks bloody weird?
Also, when you get the 2-Star crystal in the event (870 BP), it gives you story dialogue.