I can’t confirm one way or the other for that piece specifically, as I never tried it, but all of the special effects can think of that I have seen work equally well on thralls.
Give this armor to a thrall and place it against a queen reaper. You don’t have to do it online, go single player and use the admin panel. Use a Berserker, they are vulnerable to poisoning. Last time I placed 5 Berserkers (spawned straight from admin panel, no armor only their sword and exotic feast for heal) against the scorpion in the darfari lands, the scorpion rekt all five of them.
Anyway, I will try it later to confirm, as @Tephra said I never done it .
Each of the Champion’s and Godbreaker set pieces give some sort of special bonus - except for the gloves (the gloves used to give extra attribute points, but they were nerfed with the thrall update and are no longer special).
The Champion’s set bonuses are focused around curing debuffs.
OK, I runned some tests on single player…
Arena champion armor, to whole thralls is better than redeemed silent legion even if it has lower armor points on poisoning. Even when I placed the God breaker helmet and removed the arena helmet, the thrall end up better with the arena set. However in bleeding the redeemed was better than the arena, which means that the armor amount works better on bleeding . Berserker 0 level is very vulnerable on poisoning however the Arena suit worked properly with him. It’s pointless to say that Spinas and Dalinsia reacted perfectly on level 0 and made the fight piece of cake, they lost less than 1800 hp both against queen reaper and confessor (end boss daggon). Arena champion armor however did not react as expected, since the negative status effects were lasting the seconds they should and the armor didn’t removed them faster.
Closing, Arena champion armor is extremely good for thralls yet not cheap, it needs 50 armor scraps, at least 2 good rounds on the dungeon and we all know how risky this is on pvp servers.
So my tip is to focus on volcano thralls who starts with exceptional stats on survival and hp, which make them less vulnerable on poisoning and bleeding. Perks matters a lot, so don’t cry for a survivalist perk, it’s good .