Clerics are mostly casters in my view and especially important for me is the concentration slot because there are fantastic spells available. A cleric without a shield for me is wasted potential, given how difficult it is in the game to keep concentration. That would be also the case if you went Tempest or War domain and gave them heavy armor proficiency. In my EA Shadowheart carried, in addition to a shield, a spear which gave her advantage against the target when missing, until I got the mace which casts Fairy Fire on the target when missing. And she missed a lot, thankfully, but using profane weaponry is not her task anyway. For simpler fights she was very good with the crossbow.
I'm tempted to change her subclass to Tempest domain, as lightning (and cold) is by far the most effective magic in the game. Is it absolutely impossible from the lore to justify the Tempest domain when bowing before Shar? In that case ...
