Rex was not performing at capacity. He was acting like a very good reincarnator with a very useful skill.
He was visible enough to carry his weight in the formation but not so much that he had to explain anything later. He used telekinesis to change the direction of incoming attacks, clear away debris, and throw monsters at each other.
These are all things that a person with a strong telekinetic ability would naturally be able to do, and he didn't want to show any full power because he didn't want to risk anyone knowing the resemblance to Lustful Villain and Rex Rexilion, where both of them have the same ability.
But he knows that telekinesis isn't a rare thing, and some of them just don't know how to use it at its full potential.
Talyra shot over his shoulder twice, once with a split second's notice and once with none. Both shots hit their mark perfectly, which meant she had to know exactly where Rex's head was going to be, not where it was.
