I have been through pulls where a wipe was very possible without Temperance - tank in weak gear/trouble using CDs, weak AoE overall, people standing in crap with everything possible pulled all at once. The rest of my OGCDs gone.
*shudder*
A better healer may not need things like Temperance or Seraph in those types of situations, but it makes me feel more comfortable knowing they are there, and there are less skilled/experienced healers than me at level cap.