A key factor here is that everyone is different. What is a hard shot for one student may feel like nothing to another.
The way we approach it in our school is that you have to communicate with your training partner.
If you are geting shots that are a bit too hard, just say to that person, ' Ease up a bit will you'
Alternately, you might want to ask someone else to 'Put a bit more effort into the shot'
It can sometimes be hard to balance control and safety with preparing the body to 'take the punishment' in a real situation, but safety and common sense should always prevail.
If my Instructor was going too hard on me I'd sure as hell tell him to ease up. If I ever go too hard on a student, I'd expect, and want him to say something to me.
It's the Instructors responsibility to ensure that his class is run safely, but common sense should tell anyone to speak up if they are suffering.
If you end up training with someone who wont ease up when you ask him, speak to your Instructor after the class. If your Instructor can't resolve the situation, see your schools Chief Instructor.
To go off on a tangent, a while back I was having one of my students show a palm heel to the chest (on me), and she wasn't putting much power into it. I said to her, 'You're not stroking the cat, do it again and put a bit more effort into it'
Just after I got the searing pain in my chest I remembered she was wearing a splint on her wrist that had a metal support....
Next time I'll think before I ask her to turn up the power.
Les