I genuinely failed as an enh shaman, was hardstuck at 1.5-1.6 and blamed the MMR system, lol. But the reality was that I was not committed enough, and was expecting to be carried by others whilist not having good knowledge about my class and spec. But hey, it was easier for me to say, my team is bad, or that the MMR system is broken. (Which might be actually, as MMR jumps are weird.)