Upgrading my pyromancer

Hello !
First of all, the Grimtools link : https://www.grimtools.com/calc/L2J8B1RZ
As you can see, I have quite low OA, DA and armour compared to many other builds we can find here, and I have no clue on how I could reach reasonable values…
So far I managed to fully clear the Bastion and Valbury without much difficulty, however I fail in the other two dungeons before the boss (another casualty of this famous Manticore Deathstalker…). I welcome any advice on this topic, thanks !