My tankadin is currently good with stamina so I started working on aggro issues I got sometimes with ther tanks, specially in the taunt matter.
I know Righteous Defense and Hand of reckoning are base on melee hit (I may be very wrong, if so plz correct me) and the soft cap here is 5% for specials. I want to know if those are consider specials, since my definition for special or white hit is not very clear.
You can get away with about 6% hit. 8% is recommended for melee, but also remember paladins use a lot of holy damage. So 8% or close to it should be your goal. Hand of Reckoning I believe is based off Spell hit (the 17%). Righteous Defense however, I am not 100% sure, but from all my attempts I do not think RD can miss? You can miss from the mob being immune, but not miss by actually missing. If that makes sense.
There is no difference between paladins and warriors when it comes to threat stats. Always always always get to expertise soft cap (26). Paladins have it easy, we get 6 from a filled out Combat Expertise, and a further 10 from Glyph of Seal of Vengeance. That leaves a paltry 10 expertise to make up, easily attainable.
As of hit, I was under the impression it worked off the spell hit (even warriors run on spell hit for taunt!). However, the conversion between hit rating from gear to melee hit and spell hit are different. If you cap your specials (8%, or 263 Hit rating), this works out to 10% spell hit, leaving you with 7% hit. I've never had issues with taunts missing at that level of hit, but if it is a problem, the Glyph of Righteous Defense adds 8% hit to HoR and RD. So with 10% Spell hit and 8% from the glyph, you get 18% spell hit on taunts, more than enough to overcome the 17% spell hit miss chance against level 83 raid bosses.
Somebody ran a trial over at EJ on a DK against a dummy, having capped melee hit and 3 points in virulence (3% spell hit). I believe after 550 taunts, he missed 4% of all taunts on the 83 dummy.