I’m certain people will disagree but I have found through many purges that it just doesn’t matter enough to spend any time thinking about it. Dress them how you like. It might make a VERY slight difference if you equip archers with armor that increases Accuracy and fighters with strength perked armor. Another thing I have found in practice which no one agrees with it that the perks the thrall gets is more important then the “Archer” or “Fighter” designation. Supposedly the “multipliers” are different but in practice it’s not even detectable - or the system is broken - either way… 
All my thralls get both: Bow 30 Dmg 20 Pen, 200 Star metal arrows, and an 81 Dmg Long Sword or 2H Hammer. This now actually matters.
All thralls get nothing but Gruel for their entire lives.
DMG kits on the weapons of course but for armor I have in the past but I have found it to be a complete waste of time and materials in practice.
A lot depends on the arrangement and settings more than anything else. 90% of my thralls are set to:
- Prioritize Ranged
- Attack All Enemies
- Attack Distance 50m
- Chase Distance 15m
And the ones on walkways are set to Stand And Defend instead of Prioritize Ranged.
These settings have the thralls detecting enemies at 50m, running out away from the base 15m, taking formation there, raining arrows on the attackers, and then finishing them off with long swords and 2H hammers. Setups would be different if you were trying to acquire Purge Thralls of course. But that to me is a collector thing… like someone trying to collect all of the special weapons in the game, or all the DLC saddles, etc. It might be fun to have popular or famous names but T3 is just as good in practice - for both base defense and boss farming.
For the weapons you want a mix where some are doing Sunder, some Bleed, and some Poison - but all with 80* Dmg and 30 to 50 Pen.
You want you thralls to be placed 6M from each other all long every side of your base - I find right next to the exterior wall is best.
It also matters very little if your thralls are tier 3 or named tier 4 thralls as long as you have enough of them. Ofc, this seems to also be true when battling with a single follower - in almost every situation. A tier 3 level 10 follower will kill the Red Mother Dragon and her two babies in about 6 to 7 minutes losing only half it’s health. A tier 4 named thrall at level 20 will kill the Red Mother and her two babies in about 5 or 6 minutes losing 35 to 40% of it’s health. So like no difference - at least not enough to worry about IMO.
And I should probably mention that I mostly only have experience with Stygian thralls that come out of the wheel with about 3.5k HP and hit about 4.5K by level 10. I realize that some more primitive races may have weaker thralls but I dunno too much about them. There are three “classes” of thralls and Stygian warriors are in the middle class - offering what I consider to the the optimal balance between durability and leveling speeds.