Not using rejuvenation?

[:1]Why not?

I keep seeing posts saying to limit your rejuvenation usage, that it wastes mana. Why?

My rejuvs are healing for an average of 16.5k total and cost 4408 mana.
My HT are healing for an average of 17.8k and cost 5086 mana.

Given that data, the healing per mana for rejuv is 3.743
Given that data, the healing per mana for HT is 3.499

So, for targets who aren't in immediate danger of dying rejuv is a better option.

PLUS
Rejuv is instant cast
Rejuv can be cast while moving
You can SM a rejuv target
Nourishes/HT following a rejuv benefit from mastery.

I use rejuv as my go-to heal for dps that are under ~70 percent health. Above that I use WG+nourish, which is obviously more efficient.

Please point out if I have anything wrong or if I am missing something, or if my stats are different than most for some reason.
I've been wondering about that too, since all theorycraft shows Rejuvenation trashing Healing Touch in terms of HPM and HPCT. At 915 Haste Rating where you get the 5th tick of Rejuvenation with the 5% raid spell haste buff, it trashes Healing touch in terms of healing/cast too. My spreadsheet shows it too: http://goo.gl/sUKbE

I suspect that at some point of time, the advice "don't use rejuvenation on a party/raid target that has more than 80% health like you used to in WOTLK" got corrupted to "don't use rejuvenation at all".
The problem with rejuvenation is that it is all backend healing and you can only have it running once on a tank. Once rejuv/blooms are up on a tank you obv have to go to nourish or HT so there's that.

On raid damage, generally you need to get them to a break point quickly and rejuv is not quick at all.

In addition, it is probably the highest overheal spell in our arsenal, it can't proc living seed and did I mention it is slow?

So... you bring up valid points but you make the assumption "in situations where the target isn't in immediate danger." This assumption does not hold true for many encounters. If it did hold true, and we can make the assumption that multiple targets require non immediate healing, then you should prob just send an efflo and/or WG their way and call it a day since both of those are even more efficient.
Rejuvenation is a great spell, it just isn't spammable anymore.

You'll see more casts of HT simply because of Omen of Clarity.