in the history of D&D, the cleric had never been a DPS-master :)
his melee weapons and skills lacks of punch, his spells do very few damage (even the wrath-of-gods-like in the top levels don't match a mid-level wizard spell ...)
so IMHO, the "pure" cleric have a support role : buffing, healing, and a limited capacity to "off-tanking" ... so yes, the "pure cleric" is definitively not a killing-machine, and is not intended to
if you really want to do big damage : give up orisons and the focus weapon, take some fighter feats and a real weapon, and go rule the melee !! you'll still have the holy symbol for some spell-like (healing included) ... it won't be very easy to level divine achievements, but the "bash-skellies" should help