Discipline is a shitty tank healer, we know. Holy is even worse, we know. Of these two facts, we can agree.
My posts for both specs are like yours, in that we both view people trying to use a spanner to punch down a nail (yours are for Discipline trying to fill the tank healing role, mine are for Priests of both specs ignoring Prayer of Healing).
For a lot of those situations, a shield doesn't help as much as people think it does. Mass Shielding on aura fights (hi Lana'thel, or even better with Sindragosa) watch them fall off before those exact "oh shit" moments could really put them to use (hence where Prayer comes in before the shield, in my eyes). Using Shields to prevent some of that damage, or hold them off after it's been dealt with so they don't die is fantastic!
There is quite a large following on these forums that think Discipline should be doing nothing save for Power Word: Shield, its Glyph, and Mending. That is just as much a nail with a spanner as any other, I've seen.