Well, relative to a well geared warrior or druid our taunt will be less effective, but relative to now it'll still be more effective for us than it was before. It's about 7% less chance for taunt to be resisted (With the difference being largely affected by your gear).
I'd venture a hopeful guess and say that effectively makes normal +hit the best choice for us in case of quickly spawning adds with both Avenger's Shield and Righteous Defense now being affected by it. Doubly so for Blood Elf Paladins since if you really want to cement initial threat you just use a quick Judgement of Blood.
It's certainly worth testing, and rather makes me happy I happen to have a few items with hit rating on them; if I wear all three of those I actually have 63 hit rating (The third item, not currently equipped being a
[Pepe's Shroud of Pacification]). That should put me at about 2% taunt resist chance with Precision, quite an improvement over my current 15.3% chance of a resist (On a boss that is).
Personally I'd enjoy it if Holy Shield were changed to melee hit too, and possibly Judgement of Righteousness as well; that'd also be a smooth buff to our single target threat unless you have really high amounts of spell hit. Note that with being affected by melee hit I do mean effectively that they are treated as ranged attacks are; no parries or dodges.