I think the key to this feat is that the ally gains a +2 to damage on an attack "before the end of your next turn".
Consider two scenarios: the first, that the ally acts before the bard in the round; the second, that the ally acts after the bard.
In scenario 1, the ally bloodies an enemy, and the bard, as a free action, invokes Virtue of Valor (and Strength of Valor). Later in the round, the bard takes his turn in the initiative. He has begun his next turn.
Assuming that the ally doesn't delay (does that happen in
4e?), it means that the ally acts again before the bard, and therefore can take advantage of the bonuses.
In the second scenario, the bard acts before his ally. The ally then (on her turn in the initiative order) bloodies an opponent, and the bard, as a free action, invokes the goodies. In the following round, the bard once agains acts before the ally,
thus beginning his next turn. Then the ally gets to act again,
before the end of the bard's next turn
So it works wherever the bard is in the initiative order.
Edit: On re-reading the OP, I see that I'm assuming that, as in 3.x, a turn lasts until just before the initiative point in the following round. If that's not the case in
4e then, yes, this feat is a complete waste of time!