Imagine this scenarion:

You have Eomer with these 2 attachements (and preferably some ally died earlier in this round).

And you have 2 enemies engaged.

You defend the first one with Eomer, use Anduril to declare him as an attacker against that enemy, kill him. And since Eomer was attacking alone use the excess damage via Firefoot to trample the other enemy sucesfully avoiding his attack.

Am I right or am I missing something and this is not legal?

Seems legit to me. It's the same wording as Quick Strike.

Yeah, can't see any problems: Anduril creates an attack, Firefoot triggers off an attack. All good!

Good combo

fine, thanks

nothing is worse than if you win a scenario and then you read rules more carefully realizing you used some illegal combination.

And another excellent combo is equip one hero (I use it fo Fellowhip Aragorn) with these two cards.

After you quest succesfully, he gains one resouce and readies.