The spell says it works on all humanoids with a BR less than yours. Does it only apply to Val's? Or does it also work against humans?

If the Humanoid is not a Val, than their BR is automatically zero. As such, the wording of the spell suggests that the only ones who can withstand it are high BR Vals.

That's how I read it too. But that's potentialy very powerful ... and it also leads to some conceptual weirdness. It makes sense to me for vals to have dominion over most of "humanity" and perhaps the dwarves. Maybe even elorii, though I'm sure elorii players might howl at that thought. But Ss'ressen?

Then there are the monstrous cousins. For example the Eaters of the dead, the Gar, the Singarthans and the Voie are all humanoids. I have a hard time envisioning a Tier II val justifying to himself that the Tier III Singarthans are his "lessers" ... though I suppose higher tier creatures will be able to push through a ward fairly easily.

Tukufu will definitely have to take a had look at this spell.

On all the Val Psions I have made (as experiments) I take that spell. It is just too useful.

As to the other races, remember that unlike the Vals, NONE of them have been touched by the Divine. You could argue that Elorii have as well(actually, I'd like to see Elorii Bloodline Powers count as BR here for flavour reasons), but to the best of our knowledge no one else has. This means that the Vals are playing on their "Divine" status to empower this spell.

Is Rebuke Lesser (ARPG, p.415) an advanced spell or a sustained spell? Since the spell lists a Sustain Speed, there is no Duration listed, and the description mentions "initial casting" and "As long as the spell is active...", I suspect that it is meant to be Sustained but was mistakenly listed as Advanced Category. Which is correct?

Either way, the fix should go into future errata/FAQ.

I concur with Cody that the Eloran Bloodline Talents might count as Bloodrank, but I'm not sure whether that's a call for Henry to make or the rules staff.