What effects the follower missions you are offered?

Does player level have an effect on them?
Does the number of followers effect them?
Does the average/max level of your followers effect them?

The reason I am asking this is because I leveled to 100 at a somewhat decent pace, ended up at 100 with enough rep to buy the level 100 follower from Council of Exarchs and I find that the majority of my missions are level 96+ while overall my followers are mostly lower level then that which I feel really hampers the speed with which I can level them up.