There is a bug at Testing Grounds.
After you have passed the tests there,go back to Servant Mind and talked with it.You can see two options in the dialogue,one is "I have passed the tests", another is "What other tests are open for me?" Choose the former,and click the tick.You can see you receive 360 experience.Save the game,load the samed game,talk with Servant Mind again, still choose "I have passed the tests",gain the experience again.You can repeat this procedure infinitely and upgrade you and your group every three times until you choose "What other tests are open for me?" and save the game!
But for me, I only repeated three times. Difficulty is a part of joy of the game for me.