What does the Sunwell Offensive mean...

...to Holy Priests? Well, I'd say at the very least it can help push your reputation with Aldor over into Exalted if its not already. Thanks to some drops and one of the Hellfire Penninsula quests you can easily get 5-10 Marks of Sargeras each day. With luck you might even get a Fel Armament! This will be a slow method to get your rep up but in conjunction with regular quests you'll make it there quicker. Exalted Aldor rep will give you the nice healing shoulder enchant which is very desirable. Not only Aldor rep is gained, but SSO reputation is gained - at Exalted with SSO is a very nice and interesting healing necklace. There's some debate on how well it works and perhaps it may even be nerfed at some point, but if you haven't had much luck with decent necklaces or aren't able to raid this is a nice one to get.

Lastly, at a certain point during the Shattered Sun Offensive (Phase 3 Anvil opening at 100%) a vendor will showcase their wares for you, all of which are purchasable via Badges of Justice. There's several methods to gaining Badges and I recommend them all - Heroic instances gain you Badges off boss kills, doing the Heroic Instance daily provides you a couple more Badges as part of your reward for doing what they ask you (usually is a full clear), raid instances now drop Badges off the bosses in fact a full Karazhan clear nets you 22 Badges, and doing the SSO quests in Outlands gives you a SSO bag within which you have a roughly 10% chance of gaining said Badge. Save 'em all as the gear there is equivalent to Tier 6 and the cheapest healing gear starts at 60 Badges (ring) and goes up to 150 (weapon).

If you're not a raiding type of healer, this is an excellent way to get geared up to where the "big boys and girls" are at with their T5/6 gear. No set bonuses but the items are nice especially when gemmed up to take advantage of the socket bonuses. If you like running heroics or are already doing Kara with your guild this is a fine way to plug some equipment holes in your gear.