Agreed with Paladin instead of Cleric. You also get control undead as early as 3, allowing you to turn enemy undead into additional allies.
Rangers can certainly fill the scout role, sleight of hand and perception are the important skills (and survival and investigate to lesser degrees) and they have access to them as well as incentives to have a good Dex and Wis.
As far as healing the army, though I think oathbreaker Paladin is the better choice for several reasons, I do recommend everyone spend a day as a Cleric at 10 to ask their diety for a mace which does an AOE heal once per long rest. Until that point Druid may not be anywhere close to life Cleric but they can probably handle the healing. That and putting potions of healing on the ground, getting the wounded to surround them and blowing them up.
