Hello Mrjunior. Firstly as Argus stated, Kama solo is not a benchmark for something. Yulls are generally AOE DD's thus on single target RB's don't have the best Damage output.
Completely ignore the Krishna weapon upgrade. You need almost 100 -110 Billion to Upgrade. If you have that amount on bank, try to buy some more Basic Damage items.
Jewels : Blessed Valakas , Bless Anthy, ( Lindvior / Expensive but +10% Critic damage ) , Trasken and Tauti or Ruler ring if possible. PVE Belt / Monkey Etc.
7S Talisman is a big boost, cause combined with Longing gives you 50 more Attribute attack.
Focus on the small improvements first and slowly you will increase the damage to your desires level