About to finish ng+, as a level 154 pyromancer. I'm using the lightest possible armor (prayer robe, prayer legs, masters gloves, and the old sage's blindfold), dark estoc/pyro glove primary, and green crest shield offhand. Sage, Witch, Great Swamp, and Fire Clutch rings. 40 end, 45 int, 40 faith, 10 str, 16 dex, 20 vit, 33 vigor, 30 attunement. Puts me at 29.8% weight, 5 spell slots.
After testing lots of builds, this is by far the easiest in pve and the build I find most enjoyable in pvp. Great chaos fireball 1 shots all PvE trash, and 2 shots most difficult normal mobs. It trivializes 90% of the boss encounters. I feel like I can just run through the game at this point, dodging and hurling out hot death.
In PvP, I'm about the only "pure" pyromancer I've encountered, though lots supplement their build with it. Even though it is hardly flavor of the month (2 hand ultra weapon is the most common build I see), it does remarkably well, using great chaos fireball, flame surge, sacred flame and random 4th pyro spell (usually fire rope, fire storm, or profaned flame, but none of them are nearly as useful as the first 3).
My strategy is to start by taunting and softening them up with fire surge. Pepper them with that, then roll away twice before they can hit. This takes them out of their comfort zone, as most people want to get in close. I can generally take away 10-20% of their hp before they adjust and stop trying to run at me. At this point, most will try and pursue using circle strafe, which is my setup to hit them with Great Chaos Fireball.
The trick with GCF in PvP is to not lock onto the target and manually aim. Your goal is to shoot it a few feet in front of yourself and have your opponent run into it for massive damage. It takes skill and a bit of luck, but a hit with GCFB usually takes them < 30%. I can finish them off with a mix of the estoc/fire surge, or even sacred flame to be stylish, though that is riskier. The estoc is great for catching people off guard, it has excellent range and will often interrupt/stun bigger weapons, allowing you to roll away before getting hit. It does a surprising amount of damage, and also gives you a way to deal with shields.
Sacred flame is a scary spell, it has hyper armor frames and KO potential, and is very hard for an opponent to predict. The animation is so similar to GCF, If your opponent is dodging GCF, roll away and switch to sacred flame. You can usually catch them expecting a close quarters GCF and crush them with it.
The overall key is to maintain proper distance and use your speed advantage. Most people are sitting between 30-70% weight and will have serious problems catching you if you are quick. Fire surge can get you killed if you hold on too long, you will quickly learn to roll away rather than holding on for an extra half second. It's more practical to use to as bait for GCF then as your primary damage tool.
I'm still debating what to put in the final attunement slot. Firestorm rarely hits, has a long cast time, and leaves you extremely vulnerable. I've had people dodge the flame entirely, then hit me before I could finish the casting animation and roll away. The 4th spell is the only thing I'm still figuring out, and I may just drop to 24 attunement, though the extra mana is really nice (for one, your +10 estus gives more FP than you have total at 24 attunement, and it's nice to have some extra capacity so when you aren't totally OOM you still get the full amount of FP).
I have played and beat all the prior Souls games, and never done any PVP other than some covenant stuff. I've had a blast this last week hanging out in Pontiff Sulyvahn dueling, though I think the standard PvP level around SL 120? My build will scale down fine, so I may reroll as deprived to fix some minor stats issues and stay at SL 120. I want to work towards the sage ring +3, since it would allow me to stay at 12 dex for the estoc while maintaining full cast speed benefits.
