Blizzard does not do a good job in introducing you to the healer mini-game to begin with. It has nothing to do with dungeon difficulty on its own.
Follow these steps :
- STEP 1 : Ignore ALL DPS talents/abilities/utility.
If you can un-talent them better. If you cant, then just remove them from your bars (for now). Focus on throughput and throughput only.
- STEP 2 : Download a built-in party frames addon. Like HealBot and VohDu.
Clicking on party frames certain spells as opposed to selecting the player and pressing a button is a massive improvement in quality of life, and performance.
There are better, more sophisticated ways to use configure your UI. But, that will come later. So first, for beginners, its better to use VuhDu because 99% of the âdefaultâ setting are more than enough.
- STEP 3 : Focus on inefficient direct heals at the beginning. You dont need to follow the wow-head ârotationâ of a healer.
Many times the guides you read are too complex for a beginner. Because part of the healerâs game is also to be mana efficient. But in low keys and people learning its seccondary.
So focus on using mana inneficient direct heals and overheal a lot. Depending on the class you play. But basically you want to spend the whole combat just smashing buttons.
In the case of the RShaman for example, I have Healing Surge (fast but inneficient) and Healing Wave (slow but efficient). Just remove Healing Wave from the bar. Spam Healing Surge.
Buy yourself water and drink after every pull if you need to. In time, you will learn what is used when and become more efficient.
- STEP 4 : Ignore the haters. Part of a healers learning process is to be pro-active about incoming damage. And there is no âmagic techniqueâ to know this. You simply have to get in the dungeon, get completely wrecked by something and learn from your mistake.
Next time you do the dungeon, you will use a CD before damage comes and you will be ready for it.
And so⌠welcome to the healer club. Have FUN. 
Here is the issue : By using the built in mouse-overs you still need 1-2-3-4 buttons to cast a heal. As oposed to macroing it to the mouse click buttons.
That means that the most accessible buttons (1234) are used for spells you are literally spamming all the time.
I prefer to free up those buttons and use them for important CDs or Deffs instead, when you need lightning reflexes or someone dies.
And that is why I dont use the default blizz UI.