TD Rate is a mysterium to most S4 League players, as of now we can confirm only little knowledge about the topic itself, but what we know for sure are those things:
If your Level is below Amateur and you play in Clanwars, with enemies OVER SEMIPRO, your TD rate jumps exponentially if you reach a score above 145 ingame.
For normal games in the Free channel, the more different points you have accumulated, the higher your TDRate will jump. For example if you have 20kill points, 20pumbee points, 20defense points, 20offense points and 20 heal points, that would total 100 points, but your average would be 150. Why? Because you get additional points for the different scores you can get.
Best way is probably Station-2 6v6 without mk2 and bombs, to keep the game as long as possible, or just big s5 ruled rooms, like 4v4 or 5v5.
Good luck on getting a better TDR!
edit: If you try to farm up your rate with a multiclient, you will fail, because you would only accumulate Kill or Offensepoints and the rate will not go up, except if you put in tons of work, picking the ball with your other clients and killing them for defensepoints.