Can you identify some layouts that require display: table/table-row/table-cell? They solve some problems with CSS, but those problems (insofar as I've experienced) only come up when working with designs that specifically target the shortcomings of CSS' other display modes (e.g. your shorter secondary column has a background that needs to extend the length of the primary column); or that have layout idiosyncrasies so unconventional that a designer would either need to be familiar with how to implement them to even propose them, or be actively malicious (e.g. uh... like a variable height container that sits at the bottom of a secondary column alongside a longer primary column, I think?).
But "yes" to fast prototypes.