You could easily gem for Expertise rather than the avoidance gems you're currently using. Doing this won't only lower your avoidance stats (therefore taking more damage, therefore increasing rage), but will also cause mobs/bosses to parry/dodge you less, which will increase your threat and in turn increase your rage generation.
If your healers aren't having any trouble keeping you alive, then i would highly suggest doing this.
Edit: Remember, that as a tank, it isn't your job to take a little damage as possible. Your job is to maintain aggro on the mob/bosses so they don't go running around slaughtering your raid/group. Of course, correct spec and gear will make your healers happy.
Last edited by kroxix; 02-17-2009 at 08:47 AM.
Reason: Added information.
I agree with kroxix. No need for such avoidance. 33% block OO WOW! In a perfect world that would be awesome but there is a such thing as too much avoidance. And luckily in wow there is a balance so having such avoidance will lead to a deficiency in other areas.
Break from the wanting of so much avoidance and look at a weakness that needs fixing.