The tooltip fails to take into account many things. For example, it misrepresents the relation between crit chance, crit damange and character sheet DPS. I've caught it displaying wrong numbers many times, especially with weapons that have crit damage (either via affix or via gem).
Oh, and the tooltip also doesn't account for passives, at least not for barb's weapon master.
I seem to remember it did for Sharpshooter. Wear gloves with no DPS stats, wait for sharpshooter to stack to 100% crit, then hover over gloves with only critical chance. It should show no DPS gain. I had to remove sharpshooter in order to get accurate comparisons of gear.
You're right, I remember having to remove SS to compare gear, otherwise it would go to 100% crit and ruin the numbers.
But I'm sure the tooltip doesn't account for Weapon Master - I tested that out today. The tooltip said that a certain 2H Mighty Weapon was a 600 dps increase over a 2H Mace, when in reality it was about a 4k dps decrease, due to Weapon Master.
Not seeing where the TT is going wrong here. Of course, it's been a long day for me too... Increase in both main stat and speed along with an increase in raw weapon DPS. Now, if I would have shown the difference the TT was giving me when I went from my Skorn to my EF and Source, yeah, that was saying I would lose 44k DPS when infact I gained about 25k.
edit: Got it, see it now. As I said, long day. lol