The new target system is already difficult to adjust to, suppose it will just take time.
With that said, I don't believe it's intended for you to be able to see whomever you have targeted while they travel half way across the map. Just a few minutes ago I had a player targeted, we fought for about 10 minutes to no avail (time to kill is far too high now, IMO) until we both parted ways. The other player made it literally across the entire area we were in yet they remained targeted on my screen. With the new target system I could see them through all of the buildings and everything. Seems like a bug to me.