I have to do purely textual, non-graphic reports as part of a dashboard fairly often, usually P&L type statements, and it's not one of Tableau's strengths. I think some really minor changes would make a big difference.
I would like to see:
1. Ability to individually size columns instead of all columns resizing.
2. Ability to hide individual columns in display. If you calculate year over year differences with a table calculation, the earliest year will always have a blank column. Sometimes I need the YoY calculation on maybe six fields. Combine six blank columns with not being able to individually size columns, and you end up with a whole screen's worth of empty space.
3. Ability to use a font size smaller than 8.