I am somewhat concerned about the 3% block cost reduction medium armor will receive next patch. If BCR is thematic for medium armor is not even the problem, the issue here is math.
Before the patch, medium and heavy armor had the same maximum BCR. It was achieved with 100 point in shadow ward, golden BCR enchants, golden sturdy, fortress and Defensive Stance.
For those unaware, BCR is calculated as follows (Base cost - Flat reduction) * (1 - sturdy) * (1 - shadow ward) * (1 - passives) * (1 - actives).
This resulted in a minimum block cost of 333 (= (1750 - 609) * (1 - .32) * (1 - .25) * (1 - .36) * (1 - .10)).
Because heavy armor has better synergy with blocking, it was the better armor for this purpose.
Now for after patch.
The following does not take Survival Instinct passive into account. It assumes golden sturdy on all pieces, golden BCR enchants, highest stage of Stalwart Defender, level 2 fortress passive and Defensive Stance. Shadow ward is obviously not a thing anymore.
7 pieces of medium armor: (1750 - 689) * (1 - .32) * (1 - (.21 + .36)) * (1 - .10) = 279
7 pieces of heavy armor: (1750 - 689) * (1 - .32) * (1 - (.36)) * (1 - .10) = 414
As you can see here, the block cost in a min-maxxed heavy armor build is almost 50% higher than that of a medium armor one. And not only that. Medium armor actually has a lower minimum block cost than possible pre-patch and heavy armor became worse than before.