Stage 1
Kill all the worms which is trivial.
Stage 2
Focus on Belial and let your companions handle the little guys for the most part. Make sure at the end of this round you are full on spirit or else you'll be in much worse shape.
Stage 3
From what I can tell, Belial has 3 main abilities:
- Whack you
- Spit green stuff in sweeping motion
- Green exploding void zones
It requires a little concentration, but if you counter each one individually, it's much easier.
When he whacks you, you are in his melee range and it doesn't hit very hard, so you can basically ignore it.
When he spews green stuff, make sure you 300 life and you should live through it.
The green exploding void zones are the hard part. These will tag you for bleeding damage while you are standing in them and then they pop you for 500-600 when they explode. The only real strategy for these is to run away from them. I have found that running around the outer edge of his zone gives you the most room to work with and tends to be a lot less busy so you can see yourself the whole time.
This is not a DPS fight! Focus on keeping yourself at full life. I used the aura that heals you when you use spirit and the one that gives you 100 extra spirit. I don't think the mantras I had at this point are particularly useful for this fight, but I used the one that increases dodge to help with the first 2 stages. I also used the aura companion spell and the heal party spell. I had the enchantress follower with me.
The basic strategy is to keep your spirit capped off, and as soon as you take damage, blow some spirit. During the slow parts, run up to him and build your spirit back up. Don't forget to use your potion if you get into trouble and don't worry about your companions, they will figure it out. The last piece of advice is to not go crazy and blow all your heals when you take damage. If he hits you with a whack as you are lighting up your spirit orb or you take a green spit, just cast a single damage spell that uses spirit and save the big cool downs for when you are running away from the green voids.
Lastly, health globes do pop up in melee range quite often. It's more important to keep yourself topped off than it is to DPS.
All of the monk's healing abilities scale up with level, and not with a specific stat at all. This includes Breath of Heaven and Mantra of Healing as well.
You can also get that same "Healing from spirit spent" on certain magical Spiritstones, Daibos, and Fist Weapons.
Best Answer
Actually clicking on the enemy, instead of shift-clicking, should be enough to ensure that the attack will hit, unless you retreat too quickly; your problem seems to be that you have indeed retreated too quickly. You have to wait until the attack actually makes contact before retreating :)
How to make sure the attack lands
I think a good option will be to enable damage numbers on enemies (via the gameplay options menu). That way when you land a hit you will see the damage number floating over your enemy, and when you don't - you won't.
If you prefer to avoid that, I think the best way will be to watch for the small things that accompany damage-dealing:
I'm sure that with a little practice you'll get good in spotting these.
Increasing your range
Other than that, you can work on switching to skills that will help you land hits from further away. These include: