I actually did some calculator-ing a couple days ago to compare an elementalist/monk healer to a monk primary healer. The very first character I made back in the beta was an e/mo healer, and he's still my primary character. Here's the text file:
E/mo (assuming +20% enchantments, 12 healing and ether prodigy = 8 energy regen)
151 Heal Other for 10 energy
150 Heal Area, multiplied by (number of hurt, adjacent team-mates) minus (150 times the number of hurt, adjacent enemies) for 10 energy
192 Healing Breeze for 10 energy
67 Heal Party, multiplied by (number of hurt team-mates) for 15 energy
51, 68, 85, 102, 119, 136, 153 Dwayna's Kiss, depending on number of enchantments and hexes on ally, for 5 energy
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Remember that Ether Prodigy is, in a way, the same thing as halving ALL energy costs, and halving enemy energy-drain skills. I love getting the whole "How much energy do you have, anyway?!" comment from mesmers or rangers who don't understand Ether Prodigy.
Mo (assuming +20% enchantments, 16 healing and 15 divine = 4 energy regen)
118 Orison of Healing for 5 energy
188 Orison of Healing for 7 energy and -1 energy regen when used with Divine Boon
234 Heal Other for 10 energy
190 Heal Area, multiplied by (number of hurt, adjacent team-mates) minus (190 times the number of hurt, adjacent enemies) for 10 energy
261 Healing Breeze for 10 energy
315 Healing Breeze for 10 energy and -1 energy regen when used with Blessed Aura
84 Heal Party, multiplied by (number of hurt team-mates) for 15 energy
152 Healing Touch for 5 energy
222 Healing Touch for 7 energy and -1 energy regen when used with Divine Boon
108, 129, 150, 171, 192, 213 or 234 Dwayna's Kiss, depending on number of enchantments and hexes on ally, for 5 energy
178, 199, 220, 241, 262, 283 or 304 Dwayna's Kiss, depending on number of enchantments and hexes on ally, for 7 energy and -1 energy regen when used with Divine Boon
129 or 234 Word of Healing [Elite], depending on if your target's health is below 50% - 45 or not, for 5 energy
199 or 304 Word of Healing [Elite], depending on if your target's health is below 50% - 45 or not, for 7 energy and -1 energy regen
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Healing Touch matches the E/mo's Heal Other in energy effeciency, Dwayna's Kiss can match and exceed it given 3 or more enchantments / hexes on your target, and Word of Healing exceeds it by about +25% compared to Healing Breeze, +50% compared to Heal Other, assuming you cast it when your target's health is below 50% minus 45. Everything else is between 60-80% as effecient.
The monk primary does indeed exceed the E/mo in effeciency if the only spells he casts are those and you use two superior runes, otherwise possibly not. (Lacking a divine superior makes your Healing Touch much worse, and lacking a healing superior makes your Word of Healing much worse) This doesn't count any energy recoveries the monk's secondary class might have though, which could change things. In most cases, however, those energy regens can be much less consistant and reliable than ether prodigy.
The e/mo can, however, totally blow away Word of Healing with good use of Heal Party and Heal Area. The Heal Area would have to heal 2 people minimum, and the Heal Party 5 or 6 minimum. All in all, I'd say the e/mo is more energy effecient, especially if you want to use other skills at all, like hex removals, condition removals, armor spells, etc.
The monk primary rules more in the area of purely countering spike damage, though. If you compare his Word of Healing to the e/mo's Heal Other, it's about 10% more health over time. If you compare their Heal Others, the monk primary gets about 50% more over time. (Edit: The fact that the monk primary has more kinds of heals to carry is really what makes him better at anti-spike, I think. The e/mo is pretty much limited to those I listed for him above.)
In my opinion, it would be wisest to have both an e/mo and a mo primary for healers. Let the mo handle spiking and people with low health. The e/mo would handle healing breezes, people with high-health, the area-effect heals and condition removals. This is, of course, not the only viable way - I've learned not to think that way about this game.
But that's my input on this subject.