The problem really comes down to encounter design and the natural trade-offs in healing based on your chi generator. The vast majority of the fights require frequent amounts of aoe healing and this diminishes the amount of use of the soothing mists buff. If you are primarily jabbing, the buff does you no good at all.
This is true of every class, though. Every class is going to see more healing from their AOE (otherwise we wouldn't cast it) and if you aren't specifically assigned to ST heal you probably aren't going to use Enveloping Mists much. That doesn't mean our ST is bad.
Now, one thing about Jab - I think Monks overuse it. Jab to me is sort of the Greater Heal (or even Flash Heal) of Chi generators: its there when you need it, but you should only use it when you really need to. Unless there's a ton of damage going out, Renewing Mists, Soothing Mists, Chi Brew (or Power Strikes) give enough Chi to work with. In other words, you shouldn't depend on Jab for most of your Chi.
When I first started Mistweaving, I was Jabbing a lot and I found I had mana problems. Since then I have been relying on my ReM/Soothing Mists Chi a lot more and my mana is much better (and my numbers didn't change significantly). I still jab when I need the extra healing, or if I need some clutch Chi to keep up a Fistweaving buff or need to get TFT off, don't get me wrong!
Valen's calc in my gear(498ilvl) has Healing Sphere at 13hpm, Enveloping Mists has 10-11(17.82 with soothing as generator, 31.98 combined). This is fairly close but my enveloping tends to have similar to double my healing sphere overhealing depending on the encounter.
True, although our HOTs tick pretty fast, as well as Soothing. You may also end up Surging in there which brings down your HPM. In the real world, you're probably getting around 14-15 HPM from a Soothing/Enveloping Mists combo. That's still a pretty good efficiency level for single target.
I raid with a holy paladin and on three heal fights we use a disc priest. I don't personally think our single target is weak, it's just that in my experience, very few of the fights make me want to sit there and channel soothing for extended periods of time to use enveloping and furthermore benefit from the +30% healing buff. I would rather use the chi to uplift the raid or just chi wave(which I admit, I should use more often).
I agree, in such a comp, it makes the most sense to use the Monk for raid healing. Paladins in general go to the tanks first (but more because of beacon and their iffy raid healing rather than superior tank healing). Disc is also a strong tank healer because of how absorbs work and they are simply OP at the moment. Their AOE may be weaker in 5.2 so that will probably continue to be the case. In such a comp, the Monk heals the raid more by default than anything. That doesn't mean our ST heals are terrible, necessarily.
If a fight required nothing but tank healing the entire time I could see doing it. With the amount of raid damage going out, the importance of dps, and the bursting potential of healing sphere, I don't really see enveloping mists as a strong spell. It just has very little value unless you are already doing nothing but soothing mists. By all means use it if nothing but extended periods of just tank damage is happening, I just haven't seen it yet except for Lei Shi. I've only done five heroics.
Again, I think folks waste too much mana on Jab. Soothing works well, and you can still get decent raid healing (and yes, uplifts) out by using ReM on CD. Usually you won't use an Enveloping back to back, but it can save a tank, especially if you're already soothing him. As far as fights with significant tank damage - Will in between dances, Blade Lord p1, Wind bomb guy p1, Shek'zeer adds phase, Lei Shi, Stone Guards, Elegon (depends). If for some reason you got assigned to heal a tank, a Monk will do just fine.
I used to say the same thing on my Holy Priest back in Cata, when I tank healed several HM fights when everyone was saying how terrible Holy was at healing tanks.
Obviously, if Enveloping Mists is going to be mostly overhealing, then pop some Healing Spheres. But at that point, if you have the GCDs to use spheres (as opposed to doing AOE stuff) and you're worried your ST healing will get sniped your chance of dying is so low that it doesn't really matter what you do.
One other thing: just to reiterate, it might sound from my post like I never use/hate Jab. That is not the case. I just try as best I can to not waste mana, which means I try to get as much of my Chi as I can from spells I'm going to cast anyway, like ReM or Chi Brew. If I need to do ST healing, I'll Soothe, and if that still isn't enough I'll Jab (or most likely Surge if I need the Chi to save a tank).