I have used a Kenmore Elite induction stove after moving about 6 months ago from a gas range and it has many good qualities but no matter what I try I can't get it to heat evenly when frying food. Like when I try to sear a steak with some olive oil or stir fry something the pan ends up with a hot spot in the middle and a cool outer rim. This applies not only when heating up the pan but also in the middle of cooking it maintains this problem. This happens no matter which heating circle I use. I have tried cast iron, steel, induction element pans of various sizes, and yes they are flat,and always have this problem. I desperately need advice at this stage.
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.
Your problem here is that the induction coil is too small for your cookware. Basically, if the induction coil is 6" but your pan is 10", then you will have more heat in the middle, hence why you have noticed a hot spot in the middle.
Some types of cookware, like the All-Clad 5-ply copper core, should theoretically get around this by being very good at conducting heat and spreading it evenly. I haven't had the opportunity to try this out on an induction hob, but I can assure you that while it does conduct heat decently on an electric hob, you still need a pan that fit. I still my All-Clad cookware regardless ;)
While induction has many things going for it, you still need to consider the size of the pots/pans you will be using...
I have the same issue with a countertop single cooktop. I returned the unit thinking it was deffective only heating a 5" spot in the centre of the cooking surface of my 9" cast iron pan. New one does the same thing. The hot spot moves with pan position on the cooktop. My pan's bottom is flat, and same deal if I'm boiling water, you can see the heat is only coming from a 5" circle.
I now believe that the problem is that the coil size in the induction cooktop is just too small. I have not found a unit with a larger coil that is still 120v.
Cooking pancakes, omelettes, or even bacon if your not constantly repositioning it is so frustrating that i have gone back to my coiltop.
A lot of induction stove tops cook unevenly you should try to find reviews of it before purchasing in the future, any good review will cook a pan of sugar to show where the browning occurs and whether of not the product is worth its salt.
Cast iron and stainless steel are both poor conductors of heat, if the pans are not thick enough you will get hot and cold zones, I think you should aim for something with aluminum in it(maybe the stainless-aluminum-stainless type) and try to go for a thicker pan.
That is just my general knowledge, I didn't try induction ovens before.
edit: ignore what I said about aluminum, as JAB pointed out aluminum doesn't work with induction