I had a situation where I was trying to mimic an editable PDF. I had HTMLText for the DataCardKey's to present nice formatted Questions. No matter how meticulus I was witht he HTML the auto height would fail on one of the many fileds.
What I did was a bit interesting.
I have a Large list with all the formatted HTML questions in a sharepoint list.
Title, Body, Height, Part
Body is the HTML, Part is the PartNumber, Height is how big I want the KEY size.
I used simple lookups to pull the correct height for each DataCard. Its a static approach but its solid and the questions wont change once setup. Because the Columns were names Part1,Part2,Part3... I was able to hookup Lookups that refer to the DataField name "Part1". Because of this the same Code applied across all Datacards.
Auto height sometimes wont workout esp in HTML text controls.