You can "cheese" most missons by having at least 2 followers of the same race, and 2 of those same followers + 1 extra follower all having the same racial preference trait. Racial preferences count for more than other traits, and are just under actual counter traits, which means that for many of the bigger raid missions, you can ignore 3-4 of the available counters and just use racial traits to power through most missions.
For example. If you are alliance, you should have the human or draenei preference traits. Horde is much easier, just take orc slayer.
From questing, I got a goblin that had ally of argus, and a draenei that also had ally of argus, and I recruited another draenei that also had ally of argus from my inn. Putting all 3, will allow ally of argus to stack 3x, which gives me as much as a boost to match 2-3 counters on its own. This means on a mission that calls for something like 6 counters, like the Highmaul raid mission, I can reach 90%-100% by just matching 2 counters. It gives me as much of a benefit as matching 5 out of 6 of those encounters + the environmental bonus.
This means, if you can get 2-3 followers of the same race, each with the same racial preference, you have a team that can do every single mission You will be done with the follower game for the rest of the expac. You will not need to level any more followers to epic, you will not have to worry about getting more follower upgrades from salvage yard or warmill/bunker for the rest of the expac once those followers are max quality + ilevel.
This will carry on into future patches, if blizzard adds harder missions with more counters, you may need something like this.
Just an interesting note. You can effectively be done with followers if you can manage this. It may be worth recruiting a human with humanlover, or an orc with an orc preference rather than a 3rd scavenger or epic mount for the next few weeks. There is a chance of not having an orc follower pop up if you request the orc preference, but its worth the risk imo. You only need to have 2 followers in a mission of 3 being the specified race for all 3 buffs to pop up anyways