I don't think the whisper function is as good as it could be. You should be able to whisper to more than one person.
For example:
Three people are doing The Black Knights and they need to talk about their strategy. Since one person can only
talk to one person on the whisper tab, this makes it very difficult to have a discussion with more than one person,
as you would have to copy down what one person said to the person who didn't see it, or make the person
whispering to you whisper to the other person as well.
Allowing a person to whisper to more than one person would make group discussions a whole lot easier.
However, this does not mean a whole new design for the whisper tab. It could be as simple as having a small box
on the left of the person's name (opposite the cross) that you can tick and un-tick to select who to talk to.