^^^ You have no idea how many times I've seen those two comments:
1. "you overheal with boon"
2. "you need Offering of Blood to manage energy"
The funny thing is, they're both grossly inaccurate.
(I'm not ripping on you BTW, just those common sentiments

)
Let's tackle the first issue first (this one's easy, so I'll be brief):
The average PvE player has about 500 HP, most probably have more, but let's just say 500 HP to keep it simple. A pure healer running boon will typically have say, 14 Healing & 13 Divine Favor. Here's some quick calculations for you:
--> Orison of Healing & Boon: 63+64+42= 169 HP
So 169 would be the typical heal, which is about 1/3rd the typical player's total HP. So when they're health bar gets to about 2/3rds or lower, you heal them, and they get the full effect of the heal. How is that overhealing again?
-->World if Healing (with bonus) & boon: 170+64+42= 276 HP
276 HP is just over half of a player's total HP. For them to be receiving the bonus at all, they're health would have be down in the 1/3rd-ish range anyway, so there is not even a possibility that they won't receive the full effect of the heal. How is that overhealing again?
We can go on and on, but the fact of the matter is, using boon with 5 energy spells is certainly NOT everhealing. I'm not even going to mention 10 energy spells because every boon healer knows never to touch them.
Now the second issue (I could go on forever about this one):
First, I want you to notice the attribute point allocations I listed above (14 Healing, 13 Divine Favor), because that's what you can achieve with only minor runes by being a pure healing monk. Pure healing monk means 100% of your attribute points go into Divine Favor and Healing Prayers (with the leftovers--4 with rune--into Protection). Folks, there is no other way to put it, if you go Mo/N and dump attribute points (usually 8 or 10) into Blood Magic just for Offering of Blood, thus taking attribute points away from Healing and Divine Favor, you are a weaker healer, plain and simple. You also wasted your elite slot that could have been used on a monk elite, which makes you an even weaker healer still.
Now let's examine the rewards of being said weaker healer:
Most Mo/N net about 13 energy from OoB.
Useful? Certainly.
Needed? Almost never (and never for me)
Besides, you'll be using up that gained energy faster because you'll be duming 10 energy to heal every spike, whether it be from two 5 energy spells, or one 10 energy spell. Now I don't know about you, but I'd much rather spend 7 instead of 10.
Which brings me to another point....I get a kick out of all those "energy efficient" Mo/N's out there who bing OoB as their elite and then Heal Other for their emergency spike heal (LOL!!!), in place of World of Healing. Priceless.
But why Mo/W? Because that "W" gets you a free (as in 0 attribute points needed) 8 seconds of sprint, which is the single most underrated ability that a monk can have IMO.
It serves 2 purposes: insta-deaggro for max survivability, and extending your healing range.
Bring 7 Monk skills (please make sure 1 is a rez), and then Sprint.
I die laughing everytime I see a Mo/N or Mo/Me die and then whine about having too much aggro on them ("OMG save me stoop1d warri0r!!1").
I also die laughing everytime I see a Mo/N or Mo/Me whine about someone being too far out of their spell range to be healed in time ("OMFG y0ur to far away!1!").
I hope all that disadvantage is worth being a weaker healer.
I have never had a problem with energy.....ever (except for Glint's Crystal Wave, of course). 54 energy has always done the trick for me. And I heal more effectively than the ever-popular Mo/N's and Mo/Me.
There's no trick to it, I even posted my bar up above in this thread. Very simple; just bring boon, all 5 energy spells, and Signet of Devotion. Signet of Devotion is there for when the target's health is at or above 3/4ths. It's the perfect top off-spell. I keep it going whenever I can; I never sit still and just wait for someone's bar to drop to about 2/3rds (which then requires a real heal). I'm spamming this like crazy whenever I can.
Obviously, the key to this is to be smart about it; you don't want to get caught in a 2 second cast when people are getting spiked. With enough experience, you'll learn exactly when and when not to use Signet of Devotion. And at that point you'll find, like I did, that you'll be able to use it and conserve energy more than you realize.
bla bla bla, that's probably enough ranting, I'll shut up now.
DISCLAIMER: I was exclusively refering to PvE in this post BTW.