I've recorded a round where I was on the attacker side on the Manhattan Bridge map where I flanked and was above and behind someone corner camping a low wall. Using a well equipped carbine and no less than 2 meters away, I shot with little to no chance of missing due to the close distance and counted 12, that's TWELVE hit markers on a weapon that kills in 5 bullets up close and 6 at medium range to be turned on and killed in 3 bullets by the same player I was shooting using an LMG. The death screen showed he had a little less than half health. That means out of the 12 (twelve) shots that registered on my side (client), only 3 registered on the server. The TTD on my side was instant.
Yeah, there is a really big problem with hit detection between both clients and the server. If playing with console players is potentially the issue, DICE should give us the OPTION to disable crossplay if we want AND support PC to PC matchmaking.