Does your internal matchmaking rating go down in the event of a loss?
Yes, but different than arenas, if you are higher rated than most of your team, it will go down less. Likewise, when you win, it will go up more. This way, if you are an established good player, there’s less risk in playing with less skilled team mates. It does make the assumption that the better players tend to carry more of the weight, which may not accurate in every game, but is accurate on average.
Does MMR for RBGs function the same as it does in Arena? I.E. - goes up more when you beat a higher-rated team, and goes down more when you lose to a lower-rated team ?
Yes. MMR goes up faster if you defeat a team with a higher MMR.
What is the plan to prevent your rating from skyrocketing at high win ratios? If your rating only goes down when it is *above* your MMR, it seems that ratings will just be high on average (compared to arena)
If a team’s rating gets inflated much beyond their MMR, they will get only a few points when they win, and lose many more points when they lose, until they are back down to their MMR. This will prevent inflation.