Damn, I wonder how I could quote and answer each point of your bucket list without even reading it…
I am SS Tier at making people look stupid 
Jokes aside, I don’t know you at all, I haven’t seen your gameplay, so do not take the following statement personally because really I have no idea how you play: Amount of Time Played ≠ Skill.
→ I have played many games with a Ranked Ladder, and there is a thing we call Bronze Warriors.
Bronze, in this case, is the lowest possible rank in the ladder, and a Bronze Warrior is a player who has a massive amount of time played, but is still beyond awful at the game.
One’s play time indicates that they know about the game, but it doesn’t mean anything about their skill or lack of skill. “Madness is doing the same thing and expecting a different result.” A Bronze Warrior is someone who doesn’t adapt to get better, they keep repeating the same mistakes with the same playstyle, and they obviously keep failing, for a massive amount of time in-game.
I’m curious about the build, because maybe you got accustomed to something you think is good, or that actually was good before but which currently is not as good anymore?
In any case, I can’t say anything about your build if I don’t know it, but I will at lest provide my basic solo PvE build for reference:
Strength 1
Agility 4 - Precision Strike - Rolling Thrust
Vitality 2 - Resurgence (because Steel Thewed, otherwise don’t pick Resurgence)
Authority - 0
Grit 4 - Endurance - Steel Thewed
Expertise 1
Any Light/Medium Armor with Agility Weapon Damage Buffs.
Don’t need Heavy Armor because if you get hit by something huge, Steel Thewed limits it. Only need to watch out for DoT like Bleed and Poison, and high damage multi-hits like Rotbranch’s spin attack if you’re at its feet.
Before the Age of War, things did not hit hard, taking damage was not punishing at all, thus with high armor a Thrall was basically unkillable.
In the Age of War, they buffed most mobs’ damage, so now taking damage is punishing, and on top of Thralls being nerfed, they also are freaking stupid and will always take the damage upfront making them less viable overall.
Pre Age of War, a player got punished by running out of stamina. Thralls did not have this issue, they were never punished in PvE.
In Age of War, a player gets punished by taking damage. Thralls do have this issue, and now they are punished in PvE.
The game’s most punishing factor has shifted, thus the endgame has changed. That’s how I see it anyway.
Edit:
Healing Arrows are unfortunately a joke.
→ For the player, you just dodge most of the damage and you can disengage, heal with a potion, re-engage.
→ For followers, the healing amount is not significant enough.
↳ If you’re really looking to heal your Thrall, you need either Enhanced Gruel or Exotic Feast as food for 9 or 10 HP regen per second (don’t neglect this)
And since you’re running an Authority Build, you pick up Commanding Presence and get in there to both deal damage and heal your thrall.

For your gear, go full Skelos Cultist Master crafted with a T4 for increased Follower and Agility damage. Then of course, pick up a Legendary Agility Weapon, invest some points in Agility (I recommend maxing it out) and you suddenly have a lot of damage that will also heal up your Thrall.