Buying more energy does just add another pay to play element. But as far as the rating system goes, I feel like every game that has player rating/MMR has the same phenomenon. It's hard to move up and easy to slide down. With that said, I've been in plenty of battles in SL where I got +40 rating because I successfully punch above my weight class. It's just not going to happen when you're at the top of the leaderboard.
I get that it's frustrating to win 10 battles in a row only getting +3 rating only to have it net out to 0 after losing the 11th. That makes it harder to stay on top, mixes up the leaderboard and cements those at the top as the best, most consistent players, however. I've come to the conclusion I am neither the best, nor consistent.