I also instruct them to protest the assessed values every year on all their properties whether or not the receive an increase.

In Texas, you can protest the values but typically the purchase price is the value. 

Could it be because I protested last year on 16% increase (with no luck via HomeTaxShield)?

Since this is not an FHA loan, your best chance is to find another lender.I have successfully protested an appraisal, probably only once.  

But having 30 rentals across 6 states, I can bank on expenses being 48% to 52% annually.There are a lot of things you can do to improve your return and the two biggest things are protesting your property tax and negotiating management fees.

I wasn’t in KC but I paid my taxes under protest.

I had 30 days to protest the claim or the debt would be considered valid (the agency told me they were taping the phone conversation as I explained to them what happened with regards to my date of birth [the taped conversation becomes evidence in a court trial]).

My rule of thumb is to go ahead and tack on about 2% of the value of the home as an expense for property taxes.I have gone through the property tax valuation protest process which is fairly painless and easy when I think the county Central Appraisal District clearly has it wrong, but otherwise don't bother.  

Property tax valuations come out every spring and protests need to be filed with 30 days or May31st whichever is later

The big concern the board and the protesters had was around non-owner-occupied.