Thats pretty confusing, but likely lag honestly. The other day I found a hack guy, I invaded him and was hitting him for 56 damage using a weapon at 403 physical atack and using power within. He procceeded to kill me in one hit through my 380 armor and 900+ hp. I invaded him 2 seconds later I presume he used the dry finger, and he had adjusted his stats, he was wearing and using the same equiptment, and I now beat him silly hitting for 300 a pop and when he did connect he only took a quarter of my life.
I knocked him around a good bit, and he ran after one of my swings clipped shield but left me hanging. He dashed about 10 foot and stopped to pop an estus flask, I being used to this rushed up behind him for the backstab and as he chugged the estus flask and it made the gulp sound I died in unison with him gaining hp. You can't tell me it was lag damage, we only exchanged a few blows before he ran, and he ran for 5 or 6 seconds, far long enough for any lag damage to kick in from a swing that was never animated. The bastard had his estus flask deal area of effect damage in addition to healing him.