Why wouldn't you take on a more defensive positioning if it's near the end of the match and you're the key to the current victory?
I can understand the frustration of losing your medals at the last moment, especially as a tank. But there are means to stop this.
Being out of the way, or simply not taking all the medals on yourself. I'm seeing a lot of Ninjas taking coins. Quick movement speed without sprint, and the ability to hide and chill out in a corner somewhere holding your medals. There's no reason a tank should take everything now!