In case anyone is curious about process, I FINALLY had my arbitration hearing on the 2023 valuation (Travis County) and had it successfully reduced to what I paid for the property in 12/21.
There's definitely a learning curve with it--on ours, TCAD claimed a land value far in excess of what they could support, but that doesn't matter in arbitration--there is not (this was news to me) a burden of proof on the county at the arbitration hearing.
One thing I knew was true coming off the ARB hearing but was reiterated by the arbitrator--you need to not just undermine the county's value, you've got to articulate what you think the actual value should be (I didn't do great at that, probably partially because I'm not an appraiser).
Anyway, if someone has a question I'll try to answer it.
I think winning does make it harder to support value increases in the future, i.e., "you're telling me the value of my property rose 15%, albeit held down by the HE, but my two neighbors only rose 8%?"