My induction stove does not evenly heat a frying pan. Is it broken or am I doing something wrong?
What I would do is invest in a $30 - $50 single induction hob that can be put on your counter, and see if the problem persists there. At the worst case, you just have an extra hob for stocks or something, but it could very well be that you'll have some success there, which gives you a hob that you could use for searing and such. It helps you to eliminate the range itself as the culprit. 

The other thing you could do (again, any action here is going to cost money) is invest in some 3 or even 5 ply cookware from a vendor like All Clad. They have steel / copper / steel / aluminum / steel 'sandwich' pans that are tested to conduct heat perfectly evenly.

Given what you've tried, I tend to think the range itself is the culprit. Some induction ranges (especially earlier ones) just didn't perform very well for cooks that ventured beyond basic boiling and frying. This is why getting an extra hob might be the best course you could take. 

If it is the range itself then high-tech / high-performance layered cookware is going to probably help a little, but it's not going to fix the fact that the rings aren't functional comparable to the dispersion of a flame (which modern hobs can mostly claim, even the cheaper ones). 

While cast iron isn't guaranteed to be an even conductor and can have its issues, those issues shouldn't be nearly as bad as what you're seeing, which strongly points at the range itself as the likely culprit. 

Good luck, unfortunately this is one of those problems that requires a little spending to figure out.