Does anyone use Greater Marks of Ability Power?

No one with a brain.

A full set of Greater Marks of Ability Power give 5.31AP. If you want to do damage, penetration marks are more powerful. If you're just looking for utility scaling, AP marks are still weak. No utility scales hard enough for ~5AP to make a noticeable difference. Other marks are simply far more effective use of those slots.

You can take AD marks on an AP champ and be better off than AP marks

Magic Pen marks give about 13 pen vs 6? AP. No. No one would do this.