I tinkered around with the spreadsheet a bit this morning, adding the thundering strikes fix mentioned above, and expanding on the Trinkets section a bit to address some of what Gamaron mentioned. The "Effective" column takes into account your current hit rating and buffs as entered in the other sections. If you're, say, 50 points below 17%, the Effective column will reflect a value only giving credit for that 50 hit rating from each trinket.
If you set "Equipped" next to a trinket to 1, it will have its value added to the DPS cells for you.
This works fine for evaluating a single trinket with hit, but gets a little wierd if you're trying to evaluate two hit trinkets at once, and the combination of the two would put you over the cap.
Whoever winds up taking over the spreadsheet in the long-term, feel free to incorporate these changes (or not) as you see fit.

Other than the visible changes on the Current sheet, I added a few new cells to the EP sheet to keep the clutter off of Current, and updated the trinket table Sort macros to account for the fact that I moved those cells slightly and added the new column.
SEIC 3.2.2_Pahvel_102009
Edit: Thought occurred to me as I was driving home. If you really want to use the feature that adds a trinket's effective DEP to your DPS total, make sure you haven't included that trinket's permanent stats when you entered them (ie, enter your stat totals as they are without any trinkets equipped), or you wind up getting double credit for that particular stat.