Sorry, but I have to disagree with you... I've had plenty of PvP matches where combat did not drop after not using any attacks for 8 seconds. I'll give you some examples:
Guarding a control point in Civil War, I am constantly stuck in combat because some fool runs up, attacks, gets beat down, and then runs, no dropped combat.
Voidstar Defense, yea, try getting out of combat for that one....
Applying a DOT to another player will leave you in combat, even if they flee, sometimes even when they die (DOT persisting thru death, which I have had happen to me several times).