GrimTools: Elementalist, Level 100 (GD 1.2.0.2) - Grim Dawn Build Calculator
So I made a fun build :D. It has 5x mortar traps, 5x storm totems, all of their damage converted to lightning. It is possible to get another mortar trap, but keeping the full lightning conversion becomes a pain. Build lacks some defenses, so it’s wise to be nimble. Healing Rain, Gift of the Lotus (belt proc) and Dryad’s Blessing all help to keep you healed up while you’re dancing in the storms.
Phoenix Fire and Blast Shield help to keep damage mitigation up at key parts of the fight.
Both Mortar Traps and Storm Totems have added crit damage. You can summon 2 mortar traps at a time, and 3 storm totems at a time, so within the first second of a fight starting you have 5 summons up. 
Highest crit damage so far is 280k, likely from a “Big One” on a mortar. But considering you can have five of those hit a target at the same time, not including other sources of damage, that means that there’s a potential 2m+ per second spike damage that can occur in rare circumstances. But, one of the greatest joys of the build is that whatever damage it can do to a single target is about as much damage as it does to every target in the area. So even if it only sustains ~800k-1.2m damage most of the time (I’m guessing here), it’s dealing about that much damage to everything. Noice.
Without using Crucible summoned towers, here’s Cruci 150-170 in ~6:20
Enjoy~