I was in a pvp, I went first and the fire wizard summoned a storm minion. I took him out with an immolate, and he fled on his minion's turn. I got my 3 points, but the minion was still there. So I was battling a minion, but no person. I killed the minion, but the last time I remembered, The minion is not supposed to stay there.
If you kill a wizard and not their minion, the minion has always stayed around for that current round (and then would poof afterwards). However, just the other day I saw my life minion continue for several rounds healing others in my group after I was defeated. I don't know if that was a one time thing or not, nor if it was a bug. It is different from before though.