Thank you for the report! Since you posted this, we’ve been investigating, and following the community discussion around buff limits and missing hit chance bonuses, so I wanted to take a few minutes to post about this, and clarify what’s going on. It turns out that there are three related issues here, which made it hard to track down exactly which reports are related to which issue.
To make sense of this, I first want to talk about auras. Auras are the system that tracks persistent effects on your character, such as changes to their stats, health, critical strike chance, etc. Auras are actually divided into three distinct categories: helpful, harmful, and passive. Players are most familiar with the “16 debuff limit” which refers to the 16 available harmful aura slots. There’s a similar bank of 32 “helpful” auras, which includes things like Power Word: Fortitude, Songflower Serenade, or Rallying Cry of the Dragonslayer. And lastly there are passive effects, which include things like racial skill bonuses, or benefits gained from gear.
One confusing distinction is on “benefits from gear.” If a benefit is built into the gear, such as Wyrmhide bracers having “Increases your chance to hit by 2%” then that counts as a Passive aura, and does not consume one of your “buff slots.” However currently gear enchantments like “Greater Stats” count as Helpful auras, and do consume one of your buff slots, even though they have no visible display in your buff frame. Some players have pointed out a suspicious patch note in 1.12.1 referring to making enchantments on gear count as passive, and that clue was incredibly helpful. We found an old entry in our bug-tracking system recording a designer fixing that behavior for Burning Crusade, but the subsequent notes on that bug show that the fix was pushed live in 1.12.1. We followed that lead and did find that change in our data archives, so we’ll develop a fix for that, and mark most of the item enchantments as passive in an upcoming hotfix.
That brings us to the second issue, which is that Passive auras can also reach a limit. The limit is much higher, and we don’t believe it will ever be reached in practice, but while we were investigating these issues, we did find that we were able to reach the Passive aura limit if we did some truly ridiculous behavior, including making the world’s worst talent build. Because of that discovery, and the fact that we’re about to classify item enchantments as passive, we’re going to increase the limit for passive auras. Some of you might be thinking that this limit on passive auras is why you weren’t getting all the +hit bonuses you were entitled to, and at first we thought so too, but the level of ridiculousness needed to actually trip the passive aura limit made us suspicious. It didn’t seem likely enough to explain the number of player reports we were seeing, so we kept digging.
The third issue we found, which actually explains your lost +hit bonuses, is actually a bug in Item Set bonuses. Set bonuses that have the same benefit as item effects are actually overwriting the identical item effect, but only if the set bonus is gained after the matching item is equipped. An example is the Wyrmhide Spaulders, and the Devilsaur Armor Set bonus, which each have an incredible +2% chance to hit. If you equip both pieces of Devilsaur Armor, and then equip the Wyrmhide Spaulders, everything works fine. On the other hand, if you were already wearing the Wyrmhide Spaulders, and then equip the Devilsaur Armor, its set bonus will overwrite the Wyrmhide shoulders bonus. At that point the 2% hit bonus from the Spaulders is gone, and even unequipping the Devilsaur Armor won’t give it back. Only un-equipping and re-equipping the Wyrmhide Spaulders will fix the issue. We think this is actually the source of the +hit bonus issues, and we’re also working on a hotfix for this issue.
I really want to thank everybody who provided detailed examples and evidence because it greatly helped us in tracking these issues down, and we’ll get them all fixed as soon as we can.