I hated the tp to port after along with combat logging. I also don't like the current 30 sec invis plus super speed. Although I get it. It's basically an artificial mechanic help contend with the the OW speed. Also good to avoid being pulled into battle repeatedly. But it is abused way too much with counter tags and tagging AI fleets. A lone hunter can keep a group of a dozen guys occupied for hours and get away after killing a trader in visual range of your capital port.
The biggest problem is the RoE. A player slightly out of a circle needs to turn around and enter farther behind slower pursuers. A player with a nation port in view might not receive aid in time even with those 12 guys sitting right there unable to enter and help him.
Tag circle is fine, but give another bigger circle that all players around have a choice of joining. I mean huge like draw distance. Even give players outside of it the ability to join during the whole battle. The edge would take about an hour of sailing in battle instance to make it to the middle anyways. Split the circle in half between the tagged/tagger and joiners have to join on the edge of their half. Perhaps a special little join circle right in front of a national port that members of that nation can join from. All that and I'd be happy to keep invis/super speed. Hell even make it longer. Although no super speed of of AI's or counter tags.