They're not, but shadowheart is already a cleric and you only need one.
All the domains are cool, but none compare to life domain - all the healing spells you would want come auto prepared, every memorized slot can be offensive and CC spells, and lets face it, no one is going to use turn undead on plants or whatever, having divinity charges for a mass heal is 1 charge = 1 short rest.
Clerics *are* boring. I've been around a gaming table enough times to hear the eventual sigh, followed with "OK, I guess I'll play the Cleric." Warlock is the third most popular choice and the party already has a Warlock, too, so the argument that we don't need another Cleric is undercut by the argument that we don't need another Warlock, but Warlock is a popular choice and Cleric is not. When I say it's boring, I don't mean it's boring for everyone, just that it is boring for the majority of players. Cleric = Armor, Mace, Shield, Healing Spells. Take away armor for some builds (for something else) and make Healing part of the class abilities like I proposed above, leaving spell slots open for more interesting things, and the class becomes more interesting to more people.
