Yeah, the matchmaker just uses point values for vehicles, there's no measure of player skill for the matchmaking. I too have had matches against very good artillery players and it's a pain. And it can skew things pretty bad, especially in high tier matches. I've seen matchers there the enemy team's top vehicle was an Object 704 (best Russian tank destroyer, tier 9), and my team's top tank was a Tiger I (tier 7), because their team had more lights/low tier mediums.. but the 704 eats Tigers for breakfast, it was not a fair game at all.
Such things happen. They have at least been tweaking the matchmaker a bit here and there for the problematic vehicles, and at least in the beta the problem was that 1) there were only about 4-5k people on the US servers, and 2) they had a 5x EXP event so a ton of people jumped up multiple tiers over a weekend and it got skewed towards high tier matches, there weren't enough people still climbing up.
The early tier medium tanks do have a problem with guns, but some of them have lolcannons - terrible accuracy and penetration but high HE damage, that can still damage heavies that you can't penetrate. As you climb tiers though, guns on medium tanks get very good.