You present a very valid point. The way the White Tower traditionally trains new channelers is very inefficient. If they do not know how to handle their full power under non-stressful conditions how can you possibly expect them to bring their full power to bear when under extreme stress. Emotional control is a good thing (and when you look at how Saidar works very much required) but the shunning of channeling to do things to grow familiar with it (and at the same time accomplish the goal of finely tuned control over the weaves) seems terribly inefficient to me. While the Black Tower may focus more on teaching Ashamen to fight, the side effect is they are all very much used to working with Saidin to the point where they have very little difficulty doing both overtly large tasks and extremely small tasks with the power. I really think the White Tower could learn something from that.

On a semi-related note I wonder, if through Rand now having access to all of Lews Therins memories, we might learn that making new channelers do everything possible with the power once they learn how to embrace/seize it was the normal way of teaching in the Age of Legends.