After much frustration in Ragefire Caverns and Wailing Caverns I finally figured out why my druid wouldn't switch targets. Apparently, "/startattack focus" won't change targets if you are already attacking. Instead you have to put "/target focus" followed by "/startattack focus". Once I figured that out (about level 20) I was able to clear Wailing Caverns on my own with my 4 guys. It took a while the first time but I am now to the point where I can easily clear the whole thing in about an hour. The XP and money income from it is far better then questing 4-box so I have switched over to farming that instead.
I ended up getting my 4 characters to level 22.75 before the expansion came out and I created my Blood Elf Paladin, the 5th class in my combo. In the first night I got him up to level 15 and I'm hoping to get him to level 22 and in with my 5-man group by the end of the day. I must say, leveling in the Blood Elf starting area is so easy compared to the other starting locations. Without intimately knowing the quests I was able to beat all previous leveling time records by a long shot and I had over a gold by level 12, even with buying a weapon off the auction house (something I usually never do).
My quest to level 5 World of Warcraft characters at the same time.