The problem with the stunts in this example is that they out-compete other stunts.
Remember the Crafter Warden I mentioned?
Why should he take any accuracy-boosting stunt that isn't Swing For The Fences? From an optimization standpoint, there is no reason. And that's a problem, because it encourages one character concept above all others.
Crafter-boy would be mildly overpowered without any broken stunts. Crafter builds are pretty scary. And unlike wizards, they usually have a stunt or two.
I'm not too worried about mortals. I'm worried about people already on the edge of fairness becoming stronger.
Stunt trees are a form of controlled interaction, where the bonuses can be kept balanced. What we have here is uncontrolled interaction, which should be avoided.
PS: I'd actually like to design some more stunt trees in the future. If you check out the master list, you'll find a couple of short ones that I've made already. Your opinion would be appreciated, especially since stunt tree design is something I'm not totally comfortable with yet. I need more practice.