Tableau is currently limited to displaying 16 dimensions columns in a cross tab. There are no workarounds to this limit.
To quote Ben Schneiderman's Information Visualization: Mantra "Overview, zoom & filter, details-on-demand"
Those details on demand may included more than 16 columns. When it does, users of Tableau should expect their software to deliver for them.
I don't know what the magic number of text columns should be, but 64 sounds reasonable to be released in the next version.
*16 columns before Tableau forces concatenation of columns.
Please note, the following is a duplicate idea and it's score should be included here: