I have four large idols with “increased shadow daggers effect” on my bladedancer. Whenever I look at the tooltip of shadow daggers (skills → umbral blade → hover over ‘lethal darkness’ and press alt), the tooltip damage stays exactly the same when I put all four idols on my character, and when I remove them.
I expect the damage of shadow daggers tooltip to go up with idols inserted.
If this is the same error that you linked to then its related to the general problems with all tooltips in LE right now.
Mike W (senior dev) has mentioned these issues in a general dev blog post quite a while ago with how they are planning to fix the tooltips and character sheet info, but unfortunately updating this has been put on the backburner in favour of getting Multiplayer out…
So, yes, tooltips are buggy but the devs know about it and have plans on updating it all, they just cannot right now…