"[P]roviding advice regarding distribution planning ... would be a fiduciary act under this proposal.... The increase in the number of advisers who would be considered fiduciaries, as well as the increase in the types of services considered fiduciary acts, would significantly expand the plan sponsor's responsibilities for reviewing and monitoring outside providers. Likewise, plan sponsors would have additional responsibilities associated with reviewing and negotiating agreements with advisers to ensure they comply with general ERISA requirements and any prohibited transaction exemptions the advisers intend to use."