In my opinion, the match-making is just random enough to make it interesting, while usually guaranteeing that both sides have relative arty parity.
Outside of that, who cares? I have gotten whalloped in my small tanks by much larger tanks plenty of times, but then there are those times where the outmatched team has the luck or the skill to come out ahead of the more powerful team.
For my part, I love seeing a lot of Lowes and KV5's on the other team... usually means it is a bunch of newer players running in a tier they are not ready for.
I still haven't figured out how to discover what tier battle I am in. Is it dictated simply by the largest tank? I'll admit that I still do not have the tiers of each tank memorized.