It's been said that Yclist appears to be around UT/Undercity tier....the mask looks pretty good for the tier tbh. And let's face it, that's not a hard mob to kill by any means, UT Water is infinitely more difficult than that mob. Looking at a few of the other loots from that mob vs Arghol Bloodpyre, they seem to be about the same degree of difference loot-wise. UT and Bloodfire wing are both tier 9 per the wiki...and knowing the fights, I would call that portion of Yclist tier 9 as well.
6 AC 5 hp and 8 sta in return for 16 agility doesn't seem to be out of line to me. Between the 3 masks mentioned in this thread, all are approximately the same tier encounter. Searing Steel gives you a more dps-type option, Glare gives you the more tank-like option, and Guise is a happy medium.
Just don't confuse new content for higher tier content =\
Also I just looked at Bopper's fomelo (he's still ethereal's main warrior right?) and switching to that mask would have put him up to 6 crit vs 5, and capped his damage reduction, without uncapping his +aggression, and put his strength at 485, freeing up a buff slot b/c he would no longer need EoT for his str or sta to hit the hidden strength cap. Would have also pushed him just over 9k unbuffed hp. Yall are on crack.