^This, with the added fact that operatives are the best endurance healers as well; there have been plenty of times where the sorc healer in my raid was oof, while i was perfectly fine after some rough healing phases.
you bring up an excellent point about sorcs/sages running outta focus. And I must disagree with the point about who's better at what. I had a lovely debate about this with my guild the other day.
Everything that I say below is based upon my limited knowledge of the commando class, therefore, I cannot add anything about the commando into what I'm about to say:
I think the perfect combination of heals is a scoundrel and a sage (or class equiv. for imps).
The sage should be focusing on the tank while dropping an AOE heal as necessary.
The scoundrel should be focusing on the raid while HOTing the tank and its healer as necessary, as well as the entire raid, as much as is possible.
If you have multiple healers because you're doing an encounter like the nightmare pilgrim, the scoundrels should still be focusing on raid while assisting with the tanks.
Picture it: Everyone in the raid having constant HOTs plus the added random AOE heals from the sages.
You add to this the fact that every HOT a scoundrel has up increases their chance of getting Upper Hand.
What does upper hand do?
It gives us a heal that is FREE of charge. This heal really won't do much for a tank unless it's combined with one of the bigger heals, but if a scoundrel is NOT focusing on healing the tank, and as many people as possible have a HOT on them, then that means a scoundrel is almost always going to have the upper hand, which means nearly unlimited small free of charge heals. If this heal crits, you're looking at over 2.5k worth of healing, which is significant for any class that isn't tanking.
So if you weren't sure what perfect constant heals were for everyone in the raid, now you know.
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Now I began this with mentioning the sorc running outta juice. This is why you put them on the tank.
With a large mana pool, they have a slower regen than a scoundrel. This means, in the long run, it is harder for a sorc to see what the final outcome is with all the stuff they're doing when trying to heal everyone in the raid.
You narrow that focus to a single individual, now they're only concerned with that person staying alive. When focusing on one individual, it's easier to see how you're healing pool is reacting. When they have a better idea of how their pool is reacting, they can make better adjustments to ensure they don't run out of it by the end of the encounter.
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Now some people might want to say that the sorcs single target healing was nerfed. Sure, but the heals you'll be using on the tank aren't really any worse than a scoundrels, so you can keep the tank up, I have confidence in you.
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I don't want to make this any longer than it already is, but remember, the scoundrel can focus on lots of people because worrying about energy when it's everyone in the raid is nearly a moot point. A sage will always have to worry about it, so you limit their focus to make it easier. Further more, think about the scenario I gave you. Near everyone with HOTs, upper handed healing, and AoE healing from the sages/sorcs. Why would you say no? Why? Seriously?