When WoTLK came out it brought with it a lot more gimmick encounters, I'm alluding here to vehicle based fights. Now I was always a proponent of targettarget based macros but the vehicle based encounters severely broke them because you could no longer target your brain and had to use a focus/assist based approach. Well I was in a hurry and since a focus/assist approach is so easy to setup I threw away all my targettarget macros and did a complete switch. This worked well and although I suffered a little with focus switching lag it was successful. Then something happened with wintersgrasp, I can't remember which patch it was but suddenly noone was the raid leader, it was all automatic which meant I couldn't ask the raid leader to move my team into 1 group, why is this important padawan? you can't focus on a player who isn't in your group. Arg. It's ok until one of your team dies because they remember who was focus before joining the raid, but after death focus is cleared. So what to do?
Back to targettarget with a caveat. I switched all my macros back to targettarget and had specific macros that used focus/assist just for vehicle based encounters. This is really working well and after running with a focus system for so long I'd forgotten just how snappy the target system is. So the lesson learned here is: there is no one best way of doing something. Which is probably a good lesson for anything.