We are listening to your feedback and will keep working to improve matchmaking in the game. Right now, matchmaking is based on STRENGTH. This means that, if for example, your Tier 2 vehicle is upgraded, it will be a fair match against a Tier 3 vehicle. This explains why you can battle against vehicles of different Tiers.
I was put into a battle with a higher rank player, is this fair? Actually it is. The player's rank only reflects how much the player has played, not STRENGTH. To ensure fair matchmaking we rely solely on the STRENGTH of the vehicles, so it just depends on what vehicles players pick.
Also in survival mode when no players with similar strengths are found the matchmaking can be relaxed and enter a battle with more powerful players than you, if this happens to often you can try selecting different vehicles