Since patch 7.2, the best strategy is to split your champions' specs and counter types evenly. This allows you to keep your 7th champion as a full-time Combat Ally.
As the counter types needed for all missions are now around equal, you will generally get the best results by splitting your champions evenly with 2 of each spec and 2 of each type. Long missions (more than 8 hours) are still more common than short missions.
Note: The other Protection Warrior champion has useless abilities, so in this case it's better to activate another Fury Warrior.
Note: this is a guide to getting high mission success rates from your champions. You may find other configurations that give similar or better results, but these listed suggestions are simple to follow and should give the best results for the majority of players.
In general, for the first two slots you'll want to have the [+20% with T2 troops] item and the [+15% to all missions] item.
For the third slot, we recommend either the [+15% with T2 troops], or [+10 to all]. The [+10% to all] will pull ahead if you find you're not using the T2 troops fairly often.
Other options are the +40% to short () and +40% to long ( ) items which have more situational usefulness, but you'll often find yourself more limited in which champions to use for certain missions.
If you're lucky enough to get a legendary item with [+15% to all missions], definitely use that as a third item.
The following are the most important Order Hall Upgrades:
Getting the third Tier 2 troop is highly recommended as you'll be using them for most missions. You can take the other option when starting, but as you get Rare and Epic items from Bonus Boxes, the increased number of troops will be better in the long run.
This upgrades your Tier 2 troops, making them much stronger.
This allows you to keep a full time Combat Ally without losing any ability to do missions. Since we're working with Tier 2 troops, the other option won't help us.
The choice between these depends on your play style - neither affects mission chances.
We recommend using Meatball as your combat ally for your 7th champion, as he's a great bodyguard in the Broken Isles.
He'll drop orbs that give you a stacking damage buff up to 50% increased damage, and also will occasionally execute your targets when they're under 20%, killing them instantly in a pool of blood.