Originally Posted by Xantcha

If the tree druid that is taken into the fight does particularly well, you can simply use that as an argument as how effective we are.
If you are lacking decursers, mention that.
Go through wws and find examples of fights where guilds used two resto druids and performed exceptionally well.

Simply just talk to him, if healing is an issue and is failing after and after, then whats the harm in trying something a bit different - it may work out better. Tell him about your situation, if he doesn't know and feels that your ok with sitting out for kalec, let him know otherwise or nothing will ever happen.