FFF, as per usual has IMHO the correct view on this.
A steep turn excercise is designed to push the students confidence and handling abilities, whilst at the same time teaching how to make avoidance turns. Any comments about aerobatic manoeurvres are mis-leading, since a steep turn is not aerobatic in any way.
Advanced turning is just that, pushing the a/c a bit closer to it's limits and seeing what happens and equipping the student with the neccessary skills to control the machine.
Whether the turn is through 90 deg. or 360 isn't really relevant to the discussion. A 45 AoB level turn doesn't need any lookout over and above what the pilot should already be doing.
Just look before you act. If your lookout is good, it will be just as effective as doing all manner of HASELL checks before the excercise.