I agree wholeheartedly, placing more focus and incentivisizing 16 man raids would dramatically lengthen the player attention span in terms of PVE in this game, but my gut feeling tells me part of the reason why this is not being done is because of the additional fps issues most below average rigs experience in 16 mans -- Heroengine kind of fails whenever you clunk up more than 10 people around in an area.
This is most definitely a very frustrating part of doing 16 man operations. As a raid leader and dps I'm able to do both of my jobs with an average of 3-5 FPS in fight. It really makes the fight difficult and makes certain mechanics difficult when mobs take a much longer time to render for me. Like I said however, it's completely doable at 4 FPS on low graphic settings. (although I would love a rework so I could stop watching a slideshow!)