Overall:
Great Weaponskill Body Piece. Will defeat Grim Cuirass(+1) because of it's Increases Weaponskill Damage.
The 5% Attack is very similar to the 30/32 Attack granted VIA Grim Cuirass(+1). At 550 Attack(My average Attack) you will get 27.5 more Attack which is a little lower than Grim Cuirass but in the end, the "Increases Weaponskill Damage" is what makes this piece THE top weaponskill piece for MOST(I repeat MOST) Weaponskills.
@Daemun
WAR and BST have access to the Empyrean Axe for Cloudsplitter. This Weaponskill deals more damage with M.ATK Bonuses. This piece is easily the most godlike piece for that weaponskill.
Has a chance of dropping from Dvali Jonah, A Drergv style monster from floor 100 Nyzul Isle Uncharted, you can also trade in a Platinum Astarium (which you also obtain for beating Dvali Jonah) in exchange for this piece at the new Nyzul Isle NPC.
According to tests on BG the WS increase is +7% damage.