On second glance.Cleaver would out DPS eSoS.
Epic Sword of Shadow (base die = 2.5[2d6]):
Average Hit Damage
274.63 = 150-175(Weapon) + 112.13(Bonus)
Average Crit Damage
954.46 = 784-900.67(Weapon) + 112.13(Bonus)
Final Average Attack
464.84 = 358.33 + 106.52
Cleaver (base die = 2.5[2d8]):
Average Hit Damage
323.63 = 171.5-209.5(Weapon) + 133.13(Bonus)
Average Crit Damage
1959.29 = 1643.5-1985.5(Weapon) + 145.13(Bonus)
Final Average Attack
472.84 = 347.25 + 125.59
20th halforc with full line of epic destinies, near max'd out gear, and a base dam of about 100.
In terms of DR breakage, I see now the devs just want us to twist in the proper DR breaking powers through EDs. It was kind of wierd that every epic weapon/greensteel/cannith crafting whatever had a slot or fix to break DR and the new FR relic weapons didn't. Well just glancing over the twistable ED feats shows that anyone can break DR. Basically, the devs said "wait why would they need a slot to break DR, just let them twist it in, it's a 23rd level weapon man!? they're gonna be using EDs !"
So there you have it, it's an eSoS killer. Just glanced over too quickly.