I wouldn't go with "poor play", but instead go with us not knowing what is actually going on in the log. For all we know they could have brought to many healers and the disc was forced to do dmg instead of heal. Also it's quite common among disc priests to switch to attonement-dps if healing required is low overall, but very spikey where less healers will have a hard time. Also the log is a month old before all the nerfs/buffs.
Just to give you an example we did Madness HC yesterday. While it's doable with 2 healers, it's very rough on mana, so we went with 3 instead. The 3rd just dps' and helps here and there when required. http://www.worldoflogs.com/reports/r...?s=3848&e=4509 Almost 35% of my healing comes through attonement, am I also doing "poor gameplay"?