I'm sorry if that's an oh-so obvious thing to ask, but since figures with can use Willpower I am assuming they can use the Indomitable Feat card as well.

Am I right?

Right off of the BN PAC
- This character has the Indomitable ability
Indomitable- This character can use Willpower

By this wording, they do not possess the power, they can only use it.

That being said, it does enough to qualify for feats!- unless their Indomitable is conditional (Like Namor from SI's regeneration only being usable in water, would only allow automatic regeneration feat usable in water).