GS or Scepter/Focus
With equal power, I think you’ll get more mileage out of greatsword. The auto-attack on GSW > Scepter and scales better with power. Mirror Blade > Confusing Channel (Scepter 3) and scales better on pure power.
Berserker and Warden are somewhat situational as Berserker can move to hit more targets, but Warden is no slouch.
The other abilities are relatively worthless for DPS b/c they deal so little/no damage.
Totally would opt for GS.
It’s a well balanced weapon that really stands out. Berserker is a beast and near instant cast. Mirror Blade is wonderful. The knockback is wonderful. The number 3 skill isn’t the best, but a boon removal is a huge asset on many fights.
Scepter suffers from a few problems. The auto attack feels terribly slow and clunky. Block is a cool mechanic, but near useless when you don’t have aggro. Ray of confusion is solid damage but weak if your target doesn’t swing during the confuse duration.
GS has a whole “bit of everything” vibe where scepter is missing something to make it shine.