This seems like a really small baby step in the right direction. In a true WG style they go to ridiculous lengths to do what they perceive as the way to limit the effect of multiple arties per battle by devising a formula to reduce the chances of multiple arties perma-stunning a tank. Instead of biting the bullet and doing what they should have done from the start and limit them to one per team. Ideally they should remove all arty, but limiting them to one per team would be a compromise.