the team ability says:

When this figure takes damage from any attack, it retaliates with a magical blast that does one click of damage to the attacker...

so let's say a doombot is (copying the crossgen team ability) carrying a nebula. let's say doc samson successfully hits nebula, and nebula masterminds the damage to the doombot. does doc samson take a click of damage, since the doombot did take damage from his attack originally. (it says "any" attack.)

my guess is this isn't the case really, but would like an explanation why not.

The doombot is not taking damage from an attack but is taking damage from a power, same as why super senses is not activated when mastermind'd onto

As Mystics/CrossGen will only activate when the figure takes damage from an attack, it will not respond against Mastermind damage.

Also, for clarity, the current CrossGen/Mystics wording: