We've all done them, the quests where we at first just run around like crazy not understanding one thing about what we're supposed to do. Then we stop and read the quest text and realize, we're not supposed to understand what to do. Or if we understand it we realize it will take at least half an hour to complete it. The title says it all, there are some quests I've sworn I'll never do again. Then there are some quests you have to do if you're unlucky (just read further down and you'll see) but that I really wished they would revamp.
Blizzard have become much better at designing quests since the dawn of the game, and some quests have been removed, changed or turned into non-mandatory. Also they made a change to drop rate which means the drop rate of a quest item increases the more mobs you kill. That means eventually you'll have 100% chance to get your quest item. I wish that was true for Sida's bag.
Here are some examples of awful quests though.
A New Ore Sample
"Find an Unrefined Ore Sample on a Gravelsnout Digger or Surveyor and bring it to Tatternack Steelforge at Camp Taurajo in the Barrens."
The problem: There are like three Gravelsnout Diggers in all of Thousand Needles, and they don't even have a 100% chance to drop this. This mean you will probably have to run all around Thousand Needles several times before being lucky enough to find it. I've never managed to complete this quest before I outleveled the zone and left.
Call of Water
The shaman class quest chain to get their Water Totem.
The problem: In order to get your totem you need to visit three radically different places in Azeroth. Barrens, then Tarren Mill, back to Barrens, then Ashenvale, back to Barrens, then Silverpine Forest (out by the coast) and finally Barrens again. This at level 20. Back in the days you weren't even close to getting a mount at that level! But eventhough you can do it with a mount nowadays it still sucks badly.
Trial of Water
The druid class quest chain to get their Aquatic Form.
The problem: Although it doesn't require as much travelling as the quest Call of Water, it still requires alot of travelling. And at level 16 you don't have mount even at these times. Having to travel between Silverpine and Barrens takes alot of time if you have to run by foot. Only good thing is you can train this skill now and don't have to do the quest to get it anymore.
"Use an Evergreen Pouch with a Packet of Tharlendis Seeds and two Un'Goro Soil samples to try and cultivate samples of Morrowgrain."
The problem: Evergreen Pouch? Tharlendis Seeds? Un'goro Soil? Morrowgrain?! You want me to run around with all this crap in my bags for one quest? You don't even get a morrowgrain by every try to cultivate and the damn thing has a 10 minute cooldown. Why do quest items even have cooldown. And if you run out of Seeds or Pouches you have to buy more. Damn this quests is bad.
Digging Through the Ooze
"One of the oozes at Ironbeard's Tomb has Sida's bag, retrieve it and bring it back to her in Menethil Harbor."
The problem: Being one of the old quests this item doesn't have an increasing chance to drop. It has approximately 5% chance to drop from any of the oozes in Wetlands which means, if you're unlucky, you can get to kill many many oozes. I have gotten it on my second or so kill. I have also been forced to kill more than 50 before getting it at some times. In any case this quest sucked.
"Retrieve Helcular's Rod from the Yeti and bring it back to Novice Thaivand in Tarren Mill"
The problem: Much like with Sida's Bag, this item had a horrible droprate. In fact in the old days it had something like 0,5%-1% chance to drop. For real! Since then they've bumped the drop rate considerably though and now you usually don't have to kill more than ten or so to get the item. So this is a quest I still do actually. There are several quests who used to have quest items that just never dropped, A Recipe For Death is another good example.
I'll surely come up with more later on. Did I miss any?