For a paladin, just stack block value. Paladins can sit permanently over 102.4% avoidance with holy shield up at all times, so as long as you aren't OOM/silenced, every time you actually get hit, you should be blocking. (as long as you don't block 10 times every 8 secs, which you shouldn't be doing on a boss in any case, factoring in chances to dodge/parry/miss also).
Block value with redoubt scales any block value you have on gear up by 30%, with no diminishing returns, no matter how much you stack.
Assuming you can gear for this stat in most slots without gimping your HP or other tanking stats *too* much, you could stack block value for ridiculous amounts of melee mitigation. (I can right now tank level 80 normal instances like HoL and take literally 0 melee damage from trash - much the same in level 70 heroics for trash AND bosses)