[shatner]

A water-9 bless will get your archers to fire 50% more often (3 times every two combat rounds) so that's something. A death bless will have their arrows causing more afflictions. That's actually very synergistic with LA T'ien Ch'i since their sacred mounted archers cause AoE fear with their arrows, which stacks nicely with the common affliction of Battle Fright. Air can help since it'll make your archers more resistant to enemy archers, but it's a pretty tepid bless overall.

And that's about it. No other bless directly helps sacred archers. Of course, everything loves a little regen (nature), reinvig (earth), MR or twisted fate (astral). Note that a bonus to attack does nothing for ranged attacks and fire weapons only apply to melee, so a fire bless does literally nothing for sacred archers.