With the below glyphs, one guardian-spirit-Glyphed Holy Priest (10 second coverage, CD reduced to one min if not activated), and two 20sec/2minCD trinkets, you can continually have a trinket/CD used. 100% Uptime (even with even a little overlap from shield wall being 13 sec, not 10).
10 Sec CDs are Shield Wall and Guardian Spirit.
20 Sec CDs are Trinket1, Trinket2, and Last Stand.
Shield Block, 10 Sec CD B, 20 Sec CD F
Shield Block, 10 Sec CD C, 20 Sec CD D
Shield Block, 10 Sec CD B, 20 Sec CD E
Shield Block, 10 Sec CD C, 20 Sec CD F
Shield Block, 10 Sec CD B, 20 Sec CD D
Shield Block, 10 Sec CD C, 20 Sec CD E
This build gives you the benefit of a trinket, last stand, shield block, shield wall, or a death-preventing / heal increasing guardian spirit, at all times.
Clever use of /in macros and castsequence would make it fairly easy, and the requirement of a single holy priest is fairly reasonable for progression.
I'm pretty excited about it. Came across the idea when I was working on a Blog post about my two planned specs.