Since we are on this topic again (for the hundredth time), i'll just throw out my suggestion for dealing with combat logging that i've presented before.
Its fairly simple.
If you combat log to menu or your connection drops during a combat situation with another player, you are locked out of open mode for a certain duration (pick your duration, let's start with an hour as an example). If it happens again, you are locked out for (again, as a random number) 24 hours. Again, 1 week. Again, 1 month. There could be a decay programmed in as well, for those who "reform". So, if you go a week without CLing, you lose the first tier of penality. If you are at the 4th tier of penalty, then for a month after your lockout expires, you are still on probation, and would move up to the 5th tier (3 months lockout?), but if you then passed that month you would drop down to the 3rd tier of lockout.
It shouldn't be too hard on those who have occasional internet disconnects. Changes of it happening in combat with other players are low, and if it happens, at worse you are locked out for an hour.
If you have the sort of flakey connection which results if you losing connection so regularly it happens often during player combat situations, then really, you shouldn't be playing in Open anyway, or more to the point, any sort of online game until you get a better internet connection.
This would ultimately push those who combat log regularly to non-Open modes, reducing the frustration on those who seek PvP.