With or without a guide, running all the way to a zone to complete a few kill quests doesn't seem worthwhile to me.

As an example, Thorium Point is a popular leveling spot for Alliance with a good amount of quests. Out of the 14 or so quests about half of them are kill quests, a couple of unique item drops the whole party should be able to loot plus two escorts. The quests reward around 7,500XP each. Being generous and assuming you can complete a quest every 20 minutes, multiplied by 10 - around 3.5 hours of questing for 75,000XP. Alternatively, you could be grinding mobs in BRD for 168XP-ish per kill (300/5*1.4*2) in packs of 4-6 and earn more than double that XP in the same amount of time (while acquiring preraid BiS.)

Also, the higher level you get, the less efficient questing becomes for us. Not only do you have to deal with competition for mobs and loot in the popular leveling zones like Plaguelands or STV but constantly being ganked by higher level characters of the opposing faction.

Unless you're just a masochist and enjoy questing I don't see any reason for it outside of picking up essential quests for gear like Thrash Blade or the ring from saving the princess in BRD.