That’s a start: Archon, Level 77 (GD 1.2.1.3) - Grim Dawn Build Calculator
Obviously, there are some choices to be made both in skills and devotions.
For example, you should use a 2-handed weapon and put points into brute force for extra health and devotions into Kraken…
OR
Get a shield, and put points into safeguard.
Ideally, your main weapon could be a gun, so you can place points into Hydra (The other weapon-specific devotions don’t really help with that playstyle and damage type)
Obviously, you will also put points into Stormcaller’s pact, Divine mandate, or Path of the three, depending on the damage type you chose.
The devotion map above is made with health regen in mind, but if you’d rather go with more armor and DA, try this: Archon, Level 77 (GD 1.2.1.3) - Grim Dawn Build Calculator
The only thing that can increase the damage of GoE and Wind Devil (other than maxing their skills) are items that say " xxx (damage type) to wind devil"
There are a few more for GoE than for wind devil, but both could work.
Cyclone works great, Pyran also, but you could go vitality with Morgoneth set (Pretty hard to do in SSF playthrough, but if that specific challenge doesn’t appeal to you, this is a real possibility)
You can also go Vitality without the Morgoneth set, using Bolvar’s pendant and Pandemic Dagger.
And there is also Bartholeme’s Gavel that adds 2 summons to GoE, which is as good as increasing their damage directly (and even better in certain aspects)
I can totally echo the feeling. 
If changing character is not an issue for you, I suggest you give Blade Spirit a try. Of the 3 player-scaled pets, they are by far the most effective and they require the least points investment. They are also very easy to level: Just farm a Scarab shell periodically as you level up for absurd bleed damage. The demonslayer set is entirely craftable (well, one piece is and the rest can be transmuted) And I think the chillwhisper is the same… Both are great for endgame, though Demonslayer offers an extra summon, allows you to use the Scarab shell shield and uses a gun, which gives you access to Hydra… I have yet to try Chillwhisper fully though.
If your Passivist journey is more about the nerve damage you mentioned and not the challenge this thread proposes… and you don’t mind pressing a single button from time to time, getting just a movement medal augment will give you access to a skill to bind attack devotions to without costing you precious skill points. Personally, have remapped some of the actions slots to “scroll up” and “Scroll down” on my mousewheel, so I can have 5 different actions while still playing with just one hand. (LMB, RMB, Scrlup, scrlDown, and one of the easily reachable side button, that I generally use for evade) Sometimes, just having word of pain or curse of frailty available, while not really in-line with a full passivist character, can make a lot of difference without changing the overall feel)