All of Foe Reapers attacks are considered aoe (cleave) and can't be blocked. This means for tanks who wield shields that the damage taken will be pretty bad, at enrage I think he hits me for 40k, which is alot.
As a Warrior I loathe this boss, since you can't block his attack you basicly find your self rage starved the entire fight, and holding aggro is near impossible.