What you are experiencing is lag. Whether the source is your own connection or a function of lag comp (maybe both) is debatable. While the host connection can be a source of lag it is not the only source. Dedicated servers would only help ease some of the lag caused by people joining and leaving the match because the host wouldn't change and therefore your connection to the host wouldn't change but that doesn't mean that you would have a good connection to the server or that other folks in the lobby would have a good connection to the server. If either of these connections are bad then there will be lag effects in the game regardless of having a dedi server or not. But to your point yes it is annoying when you get shot around a corner.