People say the game is too unstable with updates reworking the game and studying data on the game is useless. These people are wrong. Why? Because the core concept of items/heros do not change with small percentage changes (ex. Sprint Boots will always improve speed) and a gamer's play style is unique enough to form patterns tied to winning and losing games.
Studying the streamers below is my evidence of this.
But past games are not accuracy to the current state of the game. You are right and I have put a half-life on older matches in relation to the date of the match to correct this.
I've done the research on these streamers to figure out what makes them good or bad and how to beat them. Come back here whenever you run into them.