Let's go with your proposed skill distribution and Power Attack.
Updating
Reave Working Draft.
Let's see, these still need weapons and armor. The original text says "However, they favor suits of garishly-decorated plate mail with flaring shoulder-plates and long chain skirts." That text plus a direct translation of the AC bonus suggests maybe a breastplate, though I wouldn't mind full plate for them.
A Breastplate is fine.
The flavour suggests they prefer heavier armour, while the movement of 9 suggests it's normally Medium armour since platemail in AD&D means Move 6 for a creature with base human speed.
Furthermore, a breastplate's +5 armour bonus matches the 5 points difference between their "base AC" of 8 and their "armoured AC" of 3, although that doesn't mean much in AD&D since armoured monsters have no firm AC rules.
As for weapons, I think the ranged one should be a javelin. For the normal monster stat block, I'm thinking one two-handed and two one-handed weapons. Something like a greataxe and two longswords maybe. Any thoughts?
Yup, I was thinking Javelins too.
As for the hand-to-hand option, the text says "typically, a reave wields two weapons" so I'd rather keep it that way rather than giving it three melee weapons.
So I'm thinking either two two-handed weapons or a two-handed weapon plus a one-handed weapon plus a shield?
Maybe a Halberd/Heavy Flair or a Flail/Longsword?
That'd be either:
Option #1*
Armor Class: 18 (+1 Dex, +2 natural, +5 breastplate), touch 11, flat-footed 17
Attack: Halberd +5 melee (1d10+3/×3); or heavy flail +5 melee (1d10+3/19-20); or javelin +3 ranged (1d6+2)
Full Attack: Halberd +5 melee (1d10+3/×3) and heavy flail +5 melee (1d10+3/19-20); or 2 javelins +3 ranged (1d6+2)
*We could use two of the same weapon, but I like the way this covers all three weapon damage types with a slashing/piercing halberd and a bludgeoning heavy flail. Since it doesn't have weapon feats there's no real benefit in pairing the same weapon.
Option #2A
Armor Class: 19 (+1 Dex, +2 natural, +5 breastplate, +1 small metal shield), touch 11, flat-footed 18
Attack: Halberd +5 melee (1d10+3/×3); or flail +5 melee (1d8+2); or javelin +3 ranged (1d6+2)
Full Attack: Halberd +5 melee (1d10+3/×3) and flail +5 melee (1d8+2); or 2 javelins +3 ranged (1d6+2)
Option #2B
Armor Class: 19 (+1 Dex, +2 natural, +5 breastplate, +1 small metal shield), touch 11, flat-footed 18
Attack: Heavy flail +5 melee (1d10+3/19-20); or longsword +5 melee (1d8+2/19-20); or javelin +3 ranged (1d6+2)
Full Attack: Heavy flail +5 melee (1d10+3/19-20) and longsword +5 melee (1d8+2/19-20; or 2 javelins +3 ranged (1d6+2)