You do want to use JoL. Use Seal of Wisdom and learn the fights then keep judgement up on the boss and melee the boss also. you can also proc the mana return with your shield of righteousness also. So learning the fights is a big key to success because you can just stand behind the boss and melee with your raid. Make sure to get the relic that reduces the cost of your holy light spells. Use all your cooldowns. you have a bunch that reduce mana cost of heals and increase healing output. But melee the boss should help a lot.
Also once you are running heroics and have the hear you need from them start doing 10 man raids. You want to collect badges to start getting tier gear. Go into Vault of archavon also since those raids also drop various tier gear.