This is another one missing its spell save DC. 

It's a spell save DC 13 if you need it.

Why does this have spirit guardians and the Archpriest doesn't?

Archpriest has a similar ability that recharges. The only edge Spirit Guardians has is that it doesn't need to recharge and hits every turn while it lasts, but it probably won't last that many rounds.

Just a priest to whatever deity they worship. 

Used to be only Medium, now is Medium or Small to accommodate for the Dwarves, Halflings, Gnomes, etc. Gained two hit die, increasing health from 27(5d8+5) to 38(7d8+7). Strength score also increased from 10 to 16, increasing the modifier from +0 to +3. 

Lost proficiency in Persuasion, but gained proficiency in Perception. Used to speak any two languages, now has to speak Common and another language. 

As always, they removed the spell slots spell list. Lost Sacred Flame, Cure Wounds, Guiding Bolt, Sanctuary, Lesser Restoration, Spiritual Weapon, and Dispel Magic spellcasting. Radiant Flame action is stronger than Sacred Flame, but not Guiding Bolt. Dispel Magic and Lesser Restoration are reworked into Divine Aid, along with Healing Word and Bless. 

Lost the Divine Eminence bonus action, but gained Multiattack. Mace is changed from 3(1d6) bludgeoning to 6(1d6+3) bludgeoning plus 5(2d4) radiant. 

This priest feels more like a holy warrior rather than a priest. I thought the whole thing was that they call on divine aid, not that they can handle themselves. I also could manage the spell slots. 

Fusion time! Give them back proficiency in Persuasion, revert back to Any two languages for flavoring. Remove radiant damage from the Mace, and give them back Divine Eminence bonus action. Lastly, give them back their spell slot list and the other spells that they lost. Really complex changes and a lot of typing. 

Even easier fusion time. Just use 2014 statblocks, cause it just feel like an actual priest.