As you get higher levels, not 50, but before 50, repose is your strongest heal. There's no reason not to use it and there's no reason for DPS not to comply with you using it. You will get DPS from time to time who refuses to play right. Just make a macro that says you cast repose on non-tank targets and that it is your strongest heal. If they refuse to comply, feel free and speak up or let them die to let them know that you are the healer. They won't get away with that so easily in later instances.