Connection losses and whatnot become statistical noise over a long enough period. That said: win rate in the current tank over ~100-200 battles is far more of a performance indicator. I have a decent efficiency rating and win rate, but I'm also a shit heavy tank driver. So if I'm in a heavy, the win rate is a lie. I was actually looking through my record last night for laughs, and I did far better in a few tanks that I thought I had. And far worse in a very few. My 40% in the Cent 1 was a bit eyebrow raising, since I always thought I was just average in it, not terrible.