Turn 4 is a bit of a dps race, true, but it's not one to which the group should require the healer to contribute, especially now that so many are in full i90 or better and with a 10% echo buff.

There's fights where the healer dpsing for specific moments can really help the team by pushing a phase or helping to meet some really high dps requirements. If turn 4 is one of them, you need to find better dps or get better gear or both.