For pve is in most cases range DD best choice. Few Tanks and heals are preferred because of their mechanics.
For range dd i can tell you, that BM hunters will be easiest one. All their spells are instant so you can jump around and do dmg Even if you take barrage as talent, it can be channeled while moving.

For a tank: I personally prefer paladin because they are good at aoe and good against casters.
Demonhunters looks pretty good too. They have a huge selfhealing.

For a healer: I will take a druid in legion, because you get a battleres und with Innervate you can cast Tranquility while moving and in a group it get buffed and is 100% stronger.

So for easy pve content my team might be a pally tank druid heal and 3 hunters.