Can Legacy attack an ally (Motivational Charge), then Heroic Interception vs. the attack, taking no damage because it was his power (heroes can't be hurt by their own powers) then heal himself and his allies 1?
Heroes can most definitely be hurt by their own powers. Just look at Nightmist.
[Edit: Sorry, I didn't look at the forum name before posting. Tactics, not SotM. 
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He's talking specifically about Tactics. There is nothing i see in the rulebook that prevents this, but it seems not right
No. Heroic Interception only works during an "enemy's turn".
Aha! That's what I was missing. Thanks!