If you want to use the Dark Armour while casting Pyromancies, I tweaked your original build to look like this. Before I explain my choices, let me explain what I think you did wrong with your original build. First of all, your health is too low. Secondly, you have wasted points everywhere. You had 5 extra points in endurance with your ring setup and you had 4 points in faith but, no miracles. Your catalyst is in the wrong had for buffing and it wouldn't be for much anyway as the next chart shows so let's say you wasted another 5 points. Another waste is in your strength; why is is 25 instead of 16 for your shield? 8 Attack Rating for 9 levels is just not worth it. That gives you an outstanding 23 points wasted or 19.1% of your levels wasted.
(Right Click+View Image to see everything on the chart)
Next is your spell setup: why do you have Fire Orb selected? The additional 2 casts at the cost of damage isn't worth it. Instead take Great Fireball because you'll need the damage/larger AoE to make hitting anything meaningful/possible. On the matter of pyromancy, the idea of using a +15 flame to lower the Power Within self-damage while still being capable of dealing damage is neat. However, it just isn't worth it. The problems with your pyromancy is naivety; PvP is too cut-throat and min/max for this setup.
An innate problem with Dark Armour itself is that 40 poise is simply not a good breakpoint. Anything that you need to be afraid of stunlocking you are still going to be able to, which includes some very fast weapons on the second hit which would be hard to toggle trick out of. If you want to use the Dark Armour, you'll need to use Wolf Ring and have 80 poise. That way you'll no longer have to worry about stunlock or screwing up the toggle trick.
To fix your build I: 1) I doubled your Vitality from 25 to 50 to give you a better 1500 HP. This, although a bit lower than average, is capable of being competitive and you'll rarely have to worry about he fact your opponent has 100 more HP than you if the build is played correctly. 2) I increased your attunement from 16 to 19 for the extra spell slot. I took your endurance down from 58 to 46 to free up a considerable amount of points. I raised you Dexterity from 40 to 45 to get an increase in casting speed that pyromancy needs.* I put your Faith and Intelligence down to base because you aren't casting any miracles or spells. Since there was 1 point left over, I placed in strength for a negligible AR gain.** 3) I changed your Pyromancy Flame to a +5 Ascended one so you'll being doing more damage. 4) I changed your spell setup to Great Combustion, Great Chaos Fireball, and Chaos Fire Whip. Great Combustion and Chaos Fireball are pretty self explanatory choices. Chaose Fire Whip on the other hand is an esoteric spell. It is capable of dealing extreme damage if used correctly, with correctly being the operative word. If you stagger someone with your Chaos Fireball, you'll be capable of following up with a Chaos Fire Whip which will often give you a victory provided you can do it. 5) I changed your ring setup so it is now Wolf Ring+Havel*** so you have 80 Poise while fast rolling. 6) I changed your shield to a Grass Crest one so you'll improved stamina regeneration. Make sure to dodge those Great Combustions rather than block, and you won't miss that Black Knight Shield. 7) I gave you a Composite Bow with Poison Arrows. Although it might not look like much, it is incredibly potent. Take my word and anyone else who has used them or had it used against them, these are very powerful.
Also, all this new build does is to make a serious PvP setup that uses the Dark Armour. Note that "serious". Remember that this is just a game, and how you have fun is up to you and you alone. If you get your laughs by TWoP+WoG or running around naked after invading, that's more power to you. It is up to you to decide how you want to play, and if you have more fun playing your original build then do it. You shouldn't have to build you think isn't fun.*AR has negligible increase, it is just for casting speed
**If I placed in Vitality instead, you would have 8 more HP. It really is just a free point.
***You can switch it to Leo's ring if you are in a confident match up.