Increased join timers — due to OW travel speeds — gives a chance for everyone to receive reinforcements. It allows battles to grow bigger. Obviously, depending on how that particular battle plays out, that can be a good thing or suck. You’re holding your own right when 6 enemy ships join and turn the tide against you. That sucks. You’re barely hanging on and the cavalry arrives. Hooray!
Numerous good and complex suggestions have been made on how to deal with the whole revenge fleet, gank, or other problems associated with unrealistic OW speeds and battle join times, most of them dealing with circle size and placement, tagging, control perks, and BR limits. I suggest that right now, with the extremely low populations on both servers, we try simply increasing the join timer just to get more players involved in PVP. It would seem like it would be an easy thing for the Devs to implement and adjust. As it is, not only do you have to find a PVP situation on a very big map, you only have 3 minutes to do it.