Bulwark Talent which increases block chance after you Successfully blocked. Salvation talent reduces dmg taken by % of block. Then crush talent to increase shield dmg by a % of block.
Bulwark 20, increase 10% block for 5 seconds on block. Salvation, reduces dmg by 20% of block. Crush, increase shield dmg by 100% of block.
If 45% block added, then crush would mean shield dmg increased by 45%. Salvation would mean 9% dmg reduce in PvE and bulwark increasing the block chances by +10% so you would have 55% block once you successfully block.
Shield does have 10% block which is added once you equip it though so its more like 55% block once you added 45% block so really 55% dmg increase from crush 20 talent for shield which is large. Shield builds like bash and in general can be quite interesting for dmg at close range but also blocking often.