@Pawdraig Not established enough, in my opinion. We got the old dude dying from essentially old age. A human would not disappear in a puff of smoke if they were shot in the shoulder, so nothing established that something like that was dependent on their power level. That's basically below human power level. They also fed multiple times during the movie including right up to that encounter so there's no way they were that weakened.
@Gargron Yea, they could have gone through some injury, or fought back a bit more interestingly - or taken at least a second shot but I think they cut that scene short for brevity. There was a lot of ground to cover in that movie between the past, the resolution and further explanation of enemies\the girl - I was fine with it not being too much about a big battle, despite yeah.. expecting a little more from the demon crew.