Point of note... Chain heal is a smart heal. if you just cast it with yourself as the target it will jump (glpyhed) to the other 3 dps.
just make 2 dps buttons. one where the healer heals the tanks, 1 where the healer spams Chainheal at himself.
end result is keeping the group alive. and if you find your tank ends up in trouble. just back him so he gets clipped by the Chain heal as well.