I think that issue with your post is that you are going under the assumption that the only way to gear up as a tank is to stack Avoidance. I think you'll find around these parts that a number of tanks advocate stacking Armor/Stamina/Block Value. What this results in is taking steady smaller hits and hitting for massive numbers with Shield Slam. It's a fantastic balance as it lends itself to High Threat and a great barrier against Burst Damage.
Block Rating frankly is a very weak stat in my opinion. If you need to block you simply use Shield Block.