Even with Divine Plea, and the 2-point talent which refreshes it on a melee hit, you can oom in heroics by chain pulling.

I've untalented the ability which slows opponents melee attack speed, and unglyphed Divine Plea because I do not wish the mob to deal 3% less damage to me. Moved this glyph to Spiritual Attunement, for the extra mana received on heals. And the slight increase in damage taken, is no big deal to heal through, but it is marginally more healing received, for more mana from being healed.