Raid leadership is an interesting beast. In particular figuring out who is going to call out what and who is going to make particular decisions is a tricky sort of business that involves balancing logistical considerations with social considerations in ways that can generate a lot of drama (not to mention wipes) if it is done badly. For example, when I was leading Hounds of War, the guild I was in back in Classic WOW, I did all the raidleading. I made all the calls, organized the groups, assigned healing and such. That is, I did that until my head nearly exploded and then I got better at delegating. It was really hard to hand off healing assignments to someone else and just hope they got it all right and prevent myself from stepping in to fix things. Sometimes I am sure my idea of how it should be was actually better than the person who was doing it but many times it was just my perfectionist streak and the real difference was negligible. Obviously sometimes I must have been wrong but my memory records none of that!
The fun part about choosing who does what is often figuring out who should actually be entrusted to say things on ventrilo. Some people are really chatty and regularly sing out with information or warnings but aren't consistent; they might simply not say things at the right time, or take too long to say it, or miss it when things get sticky. Some people simply aren't interested in giving those warnings at all and will only do so under duress. The fun part comes in when you end up having someone who is very consistent and effective but who just isn't appropriate for a particular task. Sometimes you want a dpser assigning targets and calling kills and no one wants to step up so a healer does it and sometimes you have a mage telling the tanks when to swap. I find very often the ability to communicate effectively over ventrilo does not correspond well to someone's skill at playing otherwise. I have had people who made great delegates, organized groups and assignments and could report things effectively who just weren't that great at playing. They were often extremely effective when dead since they no longer had any reason to be distracted personally and could give orders and instructions to the whole raid - in fact I recall at least a few dicey kills that only went off because the guy who died happened to be able to direct the whole raid for the balance of the encounter. Of course, there are way more people of the opposite variety who play really well but can't communicate effectively at all and are utterly useless once they die.
We had this sort of situation on our Al'Alkir tries yesterday. We got him to 140k health, or about .5%. In phase 2 you have to prioritize killing adds correctly and get the timing on downing them right to maximize your damage and instead of a regular ranged dpser calling it out we had our disc priest, who is also the raid leader, doing so instead. Granted he was probably smiting them some of the time but it seems we really went with the option of getting someone who is extremely reliable and comfortable on vent and not with someone who should be spending their time watching the boss exclusively. I figure I could do it since my job in p2 is a real joke difficulty wise, but optimally we would have a ranged dps picking the targets and attacking them personally since that smooths out the time to die considerably. That isn't to say the choice was wrong, as there are plenty of considerations when choosing a person for that role and none of the ranged were clamoring for the job, but it was an example of how you have to mix the priorities of game role and real life characteristics when choosing a chooser.