You basically just said that I trade damage resistance for duration and flexibility. Sunsinger can move around too. (can even increase duration, though it's fairly short in unaltered state. Bladedancer as well, though not as long. Both of those can/do get a considerable damage bonus. If I take 4 shots to kill a normal player with a machine gun, the same amount of bullets will take down a GG at any point. Initiation as well as duration.