The relationship between uke and nage is based on harmony. "Intent" is a term that we use to describe the underlying reason for action, "I Intend to do X." I think that sometimes we forget as a martial art, the intention of keiko/training is to create conflict and resolve it. My instructor used to draw anaolgy to a scientific experiment.
To me, my partner's intent must be to create conflict. If I exist in constant harmony, how can I train to restore harmony? Hooker Sensei has lecturered on this topic on numerous occasisons - Uke brings conflict and resolves conflict, nage does only what is required to allow uke to resolve the conflict, anything more or less is not aikido. My partner can create conflict as quickly, slowly, strong, or supple as they please but conflict must be created in keiko, so it may be resolved.
Sometimes, the intensity and skill in which that conflict is created can be intimidating. Some students are not comfortable with that challenge, others look to push their comfort levels. So again, I believe that the intent of the attack should be to create conflict that should make your partner uncomfortable, but still allow them the ability to let uke resolve the technique. That intensity and skill should be appropriately managed for each student and each technique in order to create a learning environment.
Which leads me to my final observation. I think that the underlying problem in this sort of issue is not the physical attack, but the trust between partners. Keiko reinforces a relationship that demonstrates an act of trust. We give ourselves to our partner; they can break us, maim us or kill us. Every class out partners reinforce a respect for our bodies and our lives. This relationship allows us to increase our intensity and improve our comfort level in daily training. I believe that students that do not trust their partners are more uncomfortable with their partners and therefore more uncomfortable with training. Is this true all the time? Maybe not, but I think there is fair truth to the observation.