Need advice with gigaguardian 3.17 build

Hollo exiles!
Currently, I'm playing with CaptainLance9's gigaguardian its incredibly tanky but I have some problems with offence. My shaper damage is about 2kk. Literally we cant kill each other with kosis, on 20+ waves.
How I can improve my damage?
Link to guide https://www.youtube.com/watch?v=-T4ceQnQRqU&list=LL&index=1&ab_channel=CaptainLance9

which sceptre is better?