I just tested in SP with three t3 fighters(each of them has more than 2.4k hp) from volcano area with legendary weapon and armors just crushed any boss mob I spawned very easily. Archers have more hp than fighters now, but the damage is so behind compared to the fighters.
The Fighter thrall used to be useless in early EA, but now it seems they are pretty good against mobs.
Problem is these fighter guys still have no chance against other players, they are still vulnerable against dodging by players in PvP (well you can pretty much kill any NPCs or mobs by dodging). Especially, in PvE they can’t do anything but donating their stuff to the griefers 
(You won’t be able to put your fighters with great gears at outside of your base in PvE cuz players can kill your thralls but our thralls can’t even fight back yay!)