This is generally the case, but only because Feral typically does better DPS than a Protection Warrior using a 2H.
Otherwise it’d basically be:
Need defensive cooldowns - Prot Warrior
Need AoE - Prot Paladin
Everything Else - Feral Druid
Prot Warrior sucks at DPS, though, even when using a 2H or dual wielding, so you just have the Prot Warrior tank everything the Feral would most of the time.