Blizzard swung the nerf bat hard, and Holy unfortunately got whacked. This is in no small part due to the fact that Holy Paladins dominated Arenas in Season 5, with half a second Holy Lights healing for a gajillion points forcing everyone to rock back and forth in a fetal position sucking their thumbs. Healing Paladins will have to adjust to this change quite a bit, with some baseline talents adjusted, as well.
One big baseline change is how Sacred Shield can now only affect one target at a time, which lowers its versatility but redirects the Paladin back to being single target specialists. With the rework to Infusion of Light (no longer reduces cast time of Holy Light but instead increases crit chance), Paladins lose out on the fast heals, but return to large nukes that crit like monsters. The higher crit will improve sustainability through Illumination, compensating for the hardly palpable loss of Spiritual Attunement, which will become a deep Protection talent. You may not feel its loss now, but with the promised raidwide pain in Ulduar, you just might. Raiding healers will simply return to their roots -- reawakening preemptive awareness instead of the reactive mindset instilled by fast-cast nukes. It'll be just like the old days, except we've got Beacon of Light.
In PvP, things will be a little less fun. More crit on Holy Light isn't going to be of any use if you can't get to cast it. Enlightened Judgements no longer increase the range of the premiere PvP Judgement, so healers won't be able to engage right away or limit opponents' movement from afar. These nerfs along with buffs to other classes should help balance class (or spec) representation in Arenas, which started this whole nerfing nonsense in the first place.
The first big downer is that Glyph of Holy Light can no longer crit, which sucks but at least it won't be as embarrassing when a Discipline Priest posts the Overhealing Done. That said, this glyph is still our best healing glyph. So the first two Major Glyph slots are pretty much locked in with Glyph of Holy Light and Glyph of Seal of Light, but the third slot is now an interesting choice with a host of new glyphs in Patch 3.1. Seal of Wisdom might still be a contender, particularly in Ulduar, which Blizzard has specifically designed to challenge players' abilities to manage their mana.
Glyph of Divinity is going to be an extremely tempting choice, especially coupled with the reworked minor glyph, the Glyph of Lay on Hands which lowers the cooldown of our OH $#!+ button by 5 minutes. With 2/2 Improved Lay on Hands, that's a potential reset (depending on your target) every 11 minutes. That's practically every boss encounter. The new Glyph of Beacon of Light saves considerable mana, as well. There's the option to shave a second off Holy Shock's cooldown, too, so that just might float some boats. Overall, there are pretty decent choices for raiding Holy Paladins.
While the new armor sets from Ulduar may look pretty good and are definite upgrades stats-wise from T7/7.5, the set bonuses aren't so hot. Let's take a look at the 2- and 4-piece bonuses:
Your Holy Shock critical heals now also place a periodic healing effect on the target, healing for 15% of the Holy Shock's heal amount over 9 sec.
At first glance it looks cool. Paladins always get excited with Heal over Time effects. But upon closer inspection, you'll realize how much junk it is. First of all, it only procs off a crit on Holy Shock -- yet another effect that 'encourages' healing Paladins to use Holy Shock and hope it crits. I don't understand why Blizzard insists on building things around Holy Shock crits. Second, the HoT itself is piddly. I mean, it's 15% of your Holy Shock crit. I'll let you do the math, but trust me when I use the word piddly. Note that the Glyph of Holy Shock doesn't do jack for crit, so repeat after me: piddly.
Your Sacred Shield can now trigger its effect every 4 sec instead of every 6.
This was thankfully changed from the old bonus which increased Sacred Shield's effect by 10%. We're not even going to go there. This bonus, on the other hand, is pretty cool. Considering we won't be throwing out half-a-second Holy Lights anymore, the mitigation provided by Sacred Shield becomes doubly valuable. The idea is to maintain a 100% uptime for Sacred Shield, and having it proc every 4 seconds gives us a lot more breathing room. Going for the 4-piece bonus negates the 2-piece bonus of Tier 7, which increases Holy Shock crit by 10% which actually helps the 2-piece Tier 8 bonus. Funny how that works out.
Overall, Holy doesn't actually get hit that hard in PvE. It just requires a different attitude. Without the benefit of fast heals, Paladin healers will need to return to their precognitive state and throw big nuke heals ahead of time... usually on the Main Tank who's likely to get beaten down hard. The good news is that we still have access to some burst healing courtesy of Holy Shock and proc-reliant instant Flash of Lights. Just remember to keep Sacred Shield up, and things should be rosy.
In PvP, however, Holy Paladins will get taken down a proper notch, literally losing a step as casting Holy Lights will actually need a bit of juking once again. Dispellable Divine Plea also means opponents will actually manage to burn down Holy Paladin mana more efficiently (read: they actually can now). The reworked Aura Mastery brings a cooldown skill into the mix, making it more interesting. Holy Paladins will still be a force to be reckoned with in Arenas, as long as they're played right.