I only have experience with it in PvE, personally and I use it to compliment my melee and other tactics. Usually if I'm going with a pyromancy theme, I make a note to get all of the pyromancies in the game and I use fire and chaos weapons. Sometimes I even stick to Pyromancer type armor such as the rags and gold hemmed stuff. But really, the key to pyromancy is this...it doesn't scale with any stat. As long as you have at least two attunement slots (12 Attunement) you can use any pyromancy you find. This means that any and all classes can pretty much use it, regardless of what the build is and it's a versatile magic style with buffs and all kinds of things. The only thing that somewhat benefits it is Dex, which slightly (very slightly) speeds up the casting time at high levels. That's all I know.Besides that, I just find it a really cool style and I like roleplaying in Dark Souls, so it was something to play around with