Heavy stab might be overpowered but it wont match up to the DoT of a pug using flurry and mrd's base hits + WS far outweigh glads even if you are using a +3 Longsword(not aeolian because it does nothing for piercing dmg which heavy stab is).

So wearing full DD gear + choosing DD stats(str/dex) and stacking all buffs you can (Blindside, atk+ modifiers, cadence) glad wont be on 'par' with the overall output that pug/mrd will dish out. This is all assuming everyone is equally geared, matching those 3 classes side by side.