Spent some time this morning learning to put together my own auras.
So this aura has 4 layers. The first layer is just an icon to remind you to use shield block
When you use Shield block, the next layer shows the time remaining and % to crit block (in yellow)
and the last layer shows you the recharge time of shield block if you happen to exhaust both charges, which disappears once you have 1 charge and reverts to the reminder icon
here's the string:
http://pastebin.com/4vjjwcHZ
any feedback would be appreciated