honestly i think that the four scaling stats are tailored to four archetypes of play.

strength- for an all weapons build, faith- for mainly miracle builds, intelligence- for mainly sorcery builds, and dexterity- for pyromancy builds.

i think the dex stat fits with pyromancy for two main reasons: 1- it lowers casting time, which is very helpful since all pyromancies are close to mid range attacks and long cast times leave you open. 2- they're not that many dex weapons that have high scaling, i think that is because the developers expected players to have the extra damage of pyromancy. 3- (i said two earlier but i just remembered) the move set of most dex weapons meld almost perfectly with the move set of pyromancy spells. chaos fire storm and iron flesh make bows viable giving you practically unlimited poise and able to keep melee players at bay the spells great combustion and chaos fire whip flow into the move sets of the balder side sword and various spears respectively whether you need quick damage or to keep an enemy at a distance for a few crucial moments, not to mention power within which makes the speedy attacks of dex weapons into hurricanes of death.