You will need the following:
Max 70AL Armor with all blessed Insignias.
Superior Vigor
15%>50 or 15% enchanted scythe with +30HP. Other mod is optional. I guess 20% enchant wouldnt be a bad thing.

Attributes:
Mysticism: 3+1+11
Scythe Mastery: 2+10
Earth Prayers: 10+1
Skills: Mystic Sweep, Signet of Pious Light, Mystic Regeneration, Mystic Vigor, Vital Boon, Faithful Intervention, Conviction, Avatar of Balthazar [e].
Pull Faithful Intervention up and always keep it up. Next, put up Mystic Vigor, then Vital Boon, then Mystic Regeneration. Turn on Conviction and Avatar of Balthazar. Run into combat. You will have SS on you. Group the baddies into the tightest ball you can, so you strike at least 2 of them, preferrably 3. Everytime you hit ONE of them, you gain 25 HP. So if you hit 2, you gain 50. You can completely ignore SS with this build if you position correctly. mesmer will shatter you, which is why the order was important. mystic regen grants you +12 hp regen, which maxes @ 10 anyways. It has a very short recharge, coming in at only 5 secs. Vital boon is next, at a manageable 8 secs. These two are your cover enchants, and can easily be reapplied. If you are getting VERY low on HP, cast signet of pious light on yourself for a nice quick heal, and continue until u dont have enchantments left. Get Faithful intervention up ASAP, then mystic vigor, Start swinging again. Get boon and regen back up when u can. Conviction MUST stay up @ all times! Avatar of Balthazar should be used almost all the time, especially when against Abyssals.
If all goes accordingly, you should never die except maybe when facing skeletons. Kill them with Mystic Sweep and your holy dmg before they get you.
ANOTHER VARIATION:
If you want to be a pure tank, then do the following:
Reduce Scythe Mastery to 9. Take out signet of pious light and mystic Sweep.
Take your additional attribute points and add them into Earth Prayers.
Add Veil of Thorns and Armor of Sanctity. You should now not take any damage, you but you will not be able to deal much either. This is the pure tank concept.
Goodluck.