Pets can annoy you for varying reasons. A person who's a bad pet handler could easily wreck alot of havoc in any party and/or raid setting. Just the other day we had a hunter in my raid who accidentally pulled some trash in ICC with her pet. Luckily enough that particular pull didn't end in a wipe, but it easily could have! And I always forget to remove aggressive from my pet after having done Anub'Arak in AN, which always turns out funny (not). I know Love did a massive overpull on the Defias Ship in Deadmines on one of his hunters too. I still remember it although it was several years ago, just because it was so much fun seeing him play like a real noob. But this post won't be about pet handling, although that is a subject one could write quite much about. Instead I'd like to talk about pet AI, the things the pet do (and don't do) which the player who controls it (and everyone around) has little control over.
Anyone who ever plays a class which uses some sort of pet (i.e. lock, hunter or unholy dk's), will quickly notice that the sunday programmers over at Blizzard have reached new lows with some areas of the pet programming. I'm not counting the occasional pet summons, like treants or shadowfiend, but the more permanent ones. The others ones are usually not out and about long enough to get you into any real trouble.
The first problem with pets, and one of the most annoying, is when they grab a mob and run away with it like they're some love couple fleeing from justice. You really don't want to send your pet in for some tanking, and see him just keep on running, probably aggroing alot of other nasty stuff while doing it. I've actually died because of this, because when you're in a camp of mobs you don't have much maneuvering ground for that kind of behavior. Death Knights won't encounter this issue as much, since they don't use their ghouls for tanking very often.
So why does this occur and what can you do about it? Well, I can't say I know much about programming so I can't answer as to why it happens in terms of code. I have noticed however that the issue mostly arises whenever the pet has to attack a target that is already moving. So if you pull something and your pet rushes off to attack it because you've got him on defensive stance, he will engage the mob while it is on its way towards you. It seems that when the game has to calculate the pets positioning towards a moving target, which then in turn has to calculate its positioning towards the moving pet, could turn into (and mostly will turn into) this chain of running off and not stopping. There are two solutions to this problem. Either you have your pet engage the mob first, which might ease the games calculating of positions and make them stand still. This solution takes alot of waiting around for your pet to engage the mob however. Or you can bind your pet "follow" action to a key (it has a default key binding already, but I prefer to rebind it to something more available) and press it whenever he is on his way off somewhere. Just press it and then have him resume attack again almost immediately and those two should stop the running around. It's about breaking the cycle of "move" commands the server is sending those two.
The second issue is one that arises for anyone that has a summoned pet up. That is whenever a quest asks you to take control over something. That something will then count as your new pet, and this could "clash" with your current pet. I did some questing in Zul'drak on my lock and noticed that if I let a quest summon a "quest pet" for me while still having my regular pet up, I couldn't use the new pet. I had to dismiss the quest pet, resummon my pet, dismiss that one and then resummon the quest pet to make it work. Apparently the game just didn't know which pet I was using anymore!
A third issue I've noticed has only happened to my DK so far. Since I am frost specced I don't have a permanent ghoul, but one with a 3 minute cooldown. It happens, quite often I might add, that the game thinks I've got a ghoul summoned, but I clearly don't. The only way to make the game realize it's wrong so I can summon my ghoul is to relogg. Sigh...
And a fourth issue, which happens to all three pet classes but is the most annoying for a lock; whenever you get into a random instance while in the air, your pet will be desummoned when you get out of the instance again. This isn't much of an issue for a hunter or unholy DK who can just easily summon their pets again. But a lock usually has a 10 second cast time on their pets and having to do this over and over again becomes tedious. The alternative is to land and dismount from your flying mount before ever entering a random pug. Also tedious.
All this aside...since pets really own and having a pet is such a huge benefit in most areas of the game we all know hunters, locks and dk's really deserve these pet issues. Can't let them have it too easy, can we? ;)