Okay, so has title says, I *think* I have found something that may be useful to other people. First off, let me say that I don't know if this works for everybody, or even if it's commonly known already, but I didn't really search and thought I would contribute what I discovered.
So, me and my friend were playing 2's in arena. We are extremely undergeared, just getting points for the week. My friend then proceeded to die pretty quick, and then for some reason, I DC'd. I was pissed at first, but after logging back in, the arena match had ended and it said I had lost 15 points. Then, when I checked the team, the team rating indeed was 15 points lower, but I didn't lose any rating! My friend never DC'd or logged out. So curiously, I asked him next time we were about to lose to log off.
Three games later, we begin to lose, I die first, log off, then he proceeds to log off. We wait about a minute, to ensure the game has indeed ended, and log back in. We then notice that we didn't lose PR or Team Rating!
So the glitch is, if you log out when you're about to lose, wait until the arena is over (which is purely guessing how long it will take), log back in, you will not lose Team Rating or PR. I am pretty sure you will lose MMR, although I am not 100% sure, going to be testing that in a few minutes. I will let you guys know if you indeed lose MMR or not.
tl;dr: Log out of WoW when you're about to lose (both players), and team/personal rating's will remain the same. Unsure about MMR, testing soon!
edit: By logging out, I mean physically closing out of WoW. Using ALT + F4, the X at the top (in windowed mode), or any means necessary.