Isn't 0.2% smaller number than 10%, and if so wouldn't a RX (hydrocortisone) of 10% be more potent?

Yes, it is less (specifically 1/50th) but man 50 times stronger may not translate into 50 times more effective, or even twice as successful. The .2% may be as strong as it needs to be to own an effect and "the rest of the strength", so to speak, may simply be wasted.
Yes - 10% is more, however, more isn't other better.