How about something like this:
42 point buy, two flaws (really doesn't matter which ones, as they won't affect anything either way -- Noncombatant and Vulnerable?), no traits.
Human
Fighter 10
Str(16)
Dex(18 +2 Lvls)
Con(16)
Int(14)
Wis(8 )
Cha(8 )
Feats: (13)
Exotic Weapon(Greatbow)
Weapon Focus(Greatbow)
Point Blank Shot
Rapid Shot
Precise Shot
Weapon Specialize(Greatbow)
True Believer
Melee Weapon Mastery
Greater Weapon Focus
Travel Devotion
Law Devotion
Education
Knowledge Devotion
Skills:
13 ranks +2 Int +5 Skltrck +2 MWtool
Equipment
32000gp +1 Splitting Greatbow
12012gp 2x Raptor Arrows
3000gp Oil of Greater Magic Weapon(+5)
750gp Potion of Speed
Combat Performance:+36 Attack bonus (+10 BAB +5 Dex +7 Enhancement +2WF/GWF +2 RWM +4 Insight +5 Law +1 Haste)
(+34/+34)/(+34/+34) /
(+34/+34)/(+29/+29) Full Attack +Rapid Shot +Haste
20 Damage per arrow(Raptor) /
11 damage regular arrows(1d10(5.5) +2d6(7) +7 Enhancement +2 WSpl +2 RWM +4 Insight)
124 damage/round, but can Move 60' as Swift Action
keep the distance .... your Prep-time is 0 if you want to Buff-as-you-go, except applying the GMW Oil ......
if the construct gets farther than 95' from the Psion, it loses the Share Pain effect.... but if you Target the Psion, he does not have the same benifit. Target the Psion first you should be able to drop him in a single round.... only fire some of the Arrows at the Psion, since if you shoot the rest at the Construct, the Shared Damage will take out the Psion.
the Construct will not have active Direction, so you should be able to maintain the distance