It is very hard to extract the tier set calculations from the damage formulae: they are integrated into each of the appropriate TNS-* sheets.
That said, it's relatively easy to figure out how much they mean to you. Put your gear in, then hard-code the bonus state in the Advanced Infos sheet. For example, my lock has 4/4T9, so the Advanced Infos sheet shows "Tier 9 2/5 bonus" and "Tier 9 4/5 bonus" set to TRUE. When I type FALSE into the 4/5 bonus, my dps drops by 100.