For all tank classes, Accuracy is found on one set piece and Alacrity is found on one set piece in both the Arkanian and Underworld gear. These stats are found on the enhancements. Please remove these useless stats from this gear so the hardest gear to obtain is actual *useful*.
For a tank trying to maximize mitigation (highest combo of shield/defense/absorb possible) (which they should be), Best in Slot enhancements are already hard enough to get. (NONE of the pieces buyable with Elite or Ultimate comms have BiS mods or enhancements.) When you add on two of the enhancements out of the set of Arkanian/Underworld gear are completely useless, this just makes the whole thing even harder. Please remove immediately.
In case the explanation is needed: Tanks keeping aggro is not an issue at all in this game. Having abilities hit faster (alacrity) or more often (accuracy) only affects ability to keep aggro. (Most tanking cooldowns, taunts, etc are not on the Global Cooldown.) If you really feel the need to make a piece with these stats available for some reason, put it on the Elite/Ultimate comm obtainable gear, not the Arkanian/Underworld.
Good riddance.