alosso: From my experience, those MP wins leave the threshold untouched. They rather drop the average remarkably, allowing to hit the necessary average and the next tier faster.
I am sure Alosso is bang on - he always is:).............I would just emphasise how quickly it can happen though. I have seen people with 64 averages beat a Legend a couple of times and next they know....................
Nothing is ever perfect, but if any one only 1 month in to this game, say L63, is reading this it may be something to think about.