Help with Frostbolt/Vortex DPS

So i've been playing since Piety was the last boss, but I always get burnt out and take a break, but I've always kept up on uniques and general balance changes. I've had Frostbolt and Vortex MTXs in my stash for a while and want to use them, I just don't know how to go about using them properly. Like how do people get 600k+ DPS?

Such is my POB as it is

https://pastebin.com/05QLw4fG