Hum. Maybe I should rethink my stat placement. As I'm going to have to make a willpower check on a little under half my strength rolls. That cooould be a bad thing...
On the other hand, unless attacks on our will are very common, the most common way to raise will is going to be to lose control, and often raising other stats will cause will tests. So balancing starting stats is only going to be a temporary solution, since I'm pretty sure under this current system everyone is going to be constantly losing control over everything they do on everything except for stats that they seriously dumped.
Actually, in writing that last paragraph and thinking about the willpower system some more... I'm a little bit concerned that it might be not a good system. Consider a perfectly average character with 100 in all their stats. They will never have to roll willpower checks. At first. However, they will eventually raise a stat (Assuming you raise 1% at a time, could be wrong, looks more dire the faster it goes up). At that point that stat will have a... 15% chance of causing a willpower test, which seems like a pretty large jump from 0% Although this will then make willpower level up pretty fast, it still won't level up as fast as the stat, so the chance of losing control will just keep increasing. Well, depending on how many other stats the person uses in what frequency. However, even in a situation where a person uses a lot of a variety of stats, and thus manages to keep up their willpower because they are losing control in a lot of different ways, you'll still be in a odd situation where at low levels where they are their most human they will be moving between situations where they have iron control and can't possibly lose it, and where they lose control a lot. Although this situation moderates itself somewhat in that as you move to higher attunement levels the difference between attunement matters less, so then you need to have higher rolls to trigger a willpower check, that means that your willpower will be leveling up more slowly, so it will fall further behind, and even if you manage to keep it up you've got a odd system where the more monstrous someone is the better they are able to handle their monstrous impulses.
So that was a bit of a long paragraph, and my math might be wrong in some places... But, I'm a bit convinced that I don't like the willpower system, or at least I'm worried about it, it seems like control is going to be lost a lot. Although I guess it depends exactly on how hard willpower tests are. And it'll be worth seeing how it exactly works out in game. Also maybe that's the point of the system, to aim for a high rate of losing control.