30sec logoff timer would be easy and safe way to prevent combat logging. There is also abit bigger issue right now which is the server hopping for loots. There could be some sort of server hopping timer. Like they could limit the amount of server hopping to maxium 1 server change each 30mins. The system how ever should learn to spot when server did a planned maintenance reset and not reset the timer because of these. Servers are stable enough so 30mins each server change wouldn't be a problem.