"we might wipe if I dps and don't pay attention to healing" because that's a ridiculous assertion and no good player will ever be so focused on putting out damage that they'll somehow forget they're a healer...
It's very easy:

1. Be caught up to want to have all dot and Bane before dropping Cleric
2. Have a tank stand in bad they should have avoided
3. Dead tank
4. Wipe