Its not entirely based on your level, at level 98 I picked up a follower that was level 100, one of those Arakkoa constructs and I suddenly had level 100 quests.
You don't have to do a quest just because it is there. If there is little to no chance of success I place the low level followers in lower level quests.
It also helps to note your followers abilities, I have a drainei who increases success in deserts and a character that increases success when in a party with draenei. Then I have a guy that has an advantage against elementals who also doubles exp for all party members, If I see a level 100 quest in the desert against an elemental I set these three togeather and they usually succeed.
The only thing keeping me from throwing low levels in a level 100 quest for a 12% chance of success is right now I need every drop of resources and I cant waste 10 on this.