1% dodge directly effects the "bucket size" of total damage avoidance (miss, dodge and parry = NO damage to your HP). 2% shield block increases your chance to block a swing for shield block value worth of damage.

If your shield block value is 200 and the mob is hitting you for 1,000 per hit, it would take 5 blocks to equal that 1% dodge increase.

2% increase = 2 additional blocks every 100 swings for 400 damage savings. 1% dodge = 1 dodge every 100 swings for 1,000 damage savings. 10 such fights and you've saved 4,000 damage blocking vs 10,000 damage dodging...

Fight smaller bosses and it's not so steep, bigger ones and it grows larger but value wise, it remains fairly consistant that 1% dodge is worth more than 2% shield block.

Indeed the best tanker necklace in the game right now, would fit perfectly with my set right now ;)