I do know that I constantly try to improve my gear with only one end goal and that is to be viable in my guilds raid progression. We mostly do normal mode, so it's not like I *have* to go balls out and min/max everything but when things like trinkets and tier bonuses from the current tier in all difficulties (LFR, Flex, Normal) are so much better than my upgraded normal mode stuff from last tier, I feel like I should be taking all available opportunities for a chance at that gear even though it means running the same raid 3 times in any given week.
I don't know the best solution, but I do know that I hate running the same shit over and over and again, especially when I get to the point where I am cherry picking certain pieces of gear. God forbid it's on the last boss of a wing and fuck Blizzard even more when I get shit from the loot table that I absolutely don't need and have gotten 4 other times already. It actually makes me miss Valor purchased gear because at least it was a guaranteed eventuality. What I definitely don't want to happen though is them going oh hey now you can get BiS stuff from 5-mans, LFR, Flex, Normal, Heroic, Mythic, and Fuck-You modes! And it's not because I'm against 5-mans or LFR but it's because I'm against both having a chance for viable loot therefore compelling me to do both. So it almost seems like it would be a good idea to say you can get your loot via A. or B. but not both. But even then, I somehow see that going wrong and one avenue being more fruitful than the other or something stupid like that.