By now you've heard of the Orc shoulder problem (and maybe you've even confronted Azeroth's Greatest Male Orc about it), but as MMO Champion shows, that was definitely not the only major bug that showed up in 2.1.3. There's a huge list of things going wrong-- Dwarf females' offhands are huge, Blood Elf males can walk through chairs, Cyclone can prevent players from getting their BG marks (!), and ghost wolves, when attacking, can now be seen carrying weapons. What happened?!
The problem becomes even stranger when you consider the patch notes-- almost nothing got changed compared to previous patches. All we saw were a few graphical changes, an added interface option, and some high level raid tuning. As someone asked yesterday, how can all of this seemingly unrelated stuff be breaking? If all Blizzard is doing is updating the mail system, what does the size of shoulderpieces on male Orcs have to do with it at all?
The answer is probably more complicated than we can know. As commenter Okoloth said yesterday, object-oriented programming (which Blizzard uses to code the game) is full of parent/child relationships, which means that a change in one class ("wearable items in the mail") can have strange effects all across the game ("Orc shoulders shrink"). And then there's the whole fact that even though the patch notes for 2.1.3 are small, that most likely doesn't mean Blizzard is slacking-- they could be implementing more subtle changes on the system (in preparation for future content that we don't know about yet), and those changes might be having an effect on the actual game we play.
Of course, just because we aren't being told why these things are happening doesn't mean we should give Blizzard a pass on fixing them ASAP (in my opinion, they shouldn't wait until the next patch to fix my shoulder size, thank you). But just because seemingly unrelated bugs are popping up doesn't mean they don't know what they're doing.