How do you scale your damage in ruthless HC SSF ?

Hey guys !

I got a frostbreath drop so thought why not, let's try glacial hammer juggernaut. I have some decent supports: cold pen, hypothermia, momentum.
I also run the hypothermia curse, and a war banner.
Now I'm in T2 maps, and damage starts to be REALLY lacking. It's fine but a lot of rares with like life regen + resists cold are unkillable basically.

My tree is very defensive but obviously, since it's HC and I don't want to die. My only damage wheels are like starting marauder stuff, and some shield stuff for block + damage.

Ascend wise I have the action speed thing, and endurance charge (not the AOE node yet).
Wondering since I haven't played in a long time, what are the most straightforward avenues to find some potential damage upgrades here ? Like I don't know about all the new mechanics so anything more with to farm for these ?

Thanks, and just wanted to add, this is my first league playing ruthless and it is AMAZING