I, for one, am pleased to be seeing more well-reasoned replies in this thread from seasoned tanks.

Nicely done!
One of the best responses I've seen in this thread, and I agree 100%. For me, the cardinal sins of tanking are, in declining order of importance:
1) Dying
2) Losing Enmity
3) Cleaving party members
...
∞) Not doing "Big D*** DPS"
Unless the pace of a dungeon is going abysmally slow due to lackluster DPS (and let's face it, we all want to get it done and over with), I take the "safe road" and stay in Shield most of the time because I just want to clear with no hassles or drama.