Block percentage + shields

Hia, I'm just wondering how much block rating I should have currenty I have 20.60% and I'm not sure if I should keep going for block or start branching out. Here is my armory.
http://eu.wowarmory.com/character-sheet.xml?r=Silvermoon&n=Phose

Also, when I hit 80 I got the Titansteel shield wall crafted and I've been using it for a few weeks now, but a few days ago the Royal crest dropped while in strat and I started using it, but upon further inspection I realised the only thing the royal crest was giving me was 6 more stamina. The royal crest lowered all my defenseive stats, so I went back to using the shield wall, all im wanting to know is why this happened. Does +defense affect more than just your defense rating?

Sorry for the wall of text >.>

In short, Yes.

In more detail, Defense gives you bonuses to Dodge, parry, block, and miss. Lower defense means lower defensive stats.

Ok, thanks. Guess I'll be sticking with the tiansteel shield.