Maybe the % and chance is too high but I think the change is to counter those Healers that just mindlessly heal even when they don't need to. Every class has damaging spells. Of all the support types, I think Bard has the worst dps. If my Bard can throw some Coda of Fury, so can Cleric and Mages. I am pretty sure they have way more awesome damage spells.
This change makes me a bit worried too because I have the habit of just spamming Coda of Restoration simply because my Coda of Fury's damage is not impressive and I rather just keep the healing up.