No they're not. The only usefull enemy type traits are: Ogre slayer, Gronn slayer. The only usefull environment traits are: plains and marshes. Any other enemey type and environment trait is useless. Why? Because the only 4 missions that matter (Highmaul raid) have the 4 above counters.
Ontop of that some other traits like increased chance on missions above 7 hours, when fighting with other followers of a certain race etc are usefull. All other traits that dont add anything to the above 4 missions can be ignored and might aswell not exist after the initial few weeks.
The same is true for any follower combination that cant counter any of the below missions. Fpr example, any follower that counters both powerfull spell and minion swarms is useless since there is no mission that requires both. Same is true for a follower that counters AoE damage and powerfull spell, AoE damage+timed combat and Aoe damage+massive strike. Any followers that have the above ability combination can be disabled after the initial gear-up period.
http://www.wowhead.com/item=118529#missions for reference