There's also one more that spawns in the secret chamber behind a Pharros Lockstone where you get the Olenford Staff.

This is wrong. There are at least 8. 2 in the room where you summon the first npc, before the merchant. 4 in the room where you light everything up (one up top on either side of the shortcut , one on each of the drop downs). There is one in the large room that spawns the invader. And, another behind the statues in the room before the boss.

I just got a Fragrant Branch of Yore also (SOTFS: Avarice, Covetous +1, Tatters, Rusted Coin). Also, there appeared to be more than 6, and did anyone notice that the lights held by the statues in the ravine behind the sconce, go out one by one as you kill them? If I'd have know I would have counted them.

Err. 9. I forgot the one that spawns near the caster on the ledge above the entrance to the large room where the invader spawns.

Fragrant Branch of Yore drop confirmed by me too. Added to drops.

The drop section indicates the possible drops you can get by killing one of them, not guaranteed drops. The game chooses at random what they drop and they can drop the same thing multiple times. Also, armor sets aren't normally dropped all at once, you usually get one piece at a time. Farming will be required to get the other pieces (Check out the wiki page for the insolent set for more info). In order to maximize the drop rate, you should probably equip as many item discovery equipment you have and use a rusted coin before you fight one of them. Otherwise, use an ascetic of go into NG +.

Do you still need it?

Why not? enemies can drop multiple items anyway.

You're my hero dude, trying to farm the set currently.

I know how you feel. But it sure was fun fending all of them off.

They dont respawn

Do I got all 10. Fextra life said 12 and I think you're right with the outdated part.