I'm leveling a paladin, and just picked up Holy Shield. Is it common practice among protadins to macro this into regular abilities, or do you save it for when you expect high dmg? Seems like it could get very annoying in the long run with a 30s active defensive cooldown.

It's regular, but by no means optimal. While it can be annoying, using it when you're expecting more incoming blockable damage is a noticeable survivability increase (otherwise you occasionally hit stages where you pop Holy Shield and the boss isn't even hitting you for the duration). Of course, if the choice is macro it or never remember to use it, macroing it is probably a better choice for you. An unused cooldown is a worthless cooldown.

The problem with using it manually is uptime, if you're waiting too long to use it you're wasting a lot of its potential. Especially in DS most of the fights the extra damage mechanic is not blockable.

Personally I macroed it to my judgment and I just trained myself to not use my judgement when the other tank is tanking.

As for me it should be done manually all the time. For example on Warlord Zon'ozz I try not to waste it before he gets at least 4-5 stacks of focused anger or at Warmaster Blackhorn before I get at least 2 stacks of armor debuff. TellMeWhen, NeedToKnow, Raven and whatever another addon can help you to keep it up whenever it's available.

Does anyone know what healing modifiers (like the talent Divinity) effect holy radiance and if targeting a person who gets more healing means the spell does more to everyone else too? I'd test it myself but it's kind of hard to notice a few percent with RNG.

The reason I'd advise against this is is the same reason you (hopefully) don't pop GAnK/AD/DP on cooldown, or macro any of those skills to Crusader Strike. Holy Shield's strength is that it's a powerful anti-melee cooldown that's available pretty often. Don't confuse low uptime with "wasting its potential" though. It's far more important to have HS up at the right time than to have it up as much as possible.

Put another way, it doesn't matter what your Holy Shield uptime looks like as long as you survive. If I go a full minute (or two, or three) without popping it because I didn't feel threatened, that's fine. I'm far more concerned that it's available for the 15-second periods where I do feel threatened. Because that's when it'll save my life and prevent a wipe.

I have a two-part question:

1. Does switching target reset the melee swing timer? I reckon it does but still want to be sure.

2. Does the dps gain from switching target and applying (also maintaining) Censure stacks on several targets (say 2 or 3 so that we don't use DS) outweigh the dps loss of the swing timer resets (provided that the answer to #1 is 'yes')?

1. No, it does not.

Melee swing timer is normally 'front loaded'. You get your first autoattack at time zero - you engage combat and your strike occurs. After this strike your swing timer begins for attack #2. If your weapon speed is exactly 3.0 after Haste, then at time zero you strike. At time 0.001 you start counting down from 3 to a fresh attack - swapping target does not interrupt this countdown. You can autoattack target 1, tab to target 2, judge target 2, tab to target 3 and your autoattack strikes exactly 3 seconds after 1st attack - no reset.

Only a hard cast of a non-instant spell (Exo without AoW, a healing spell, etc) will reset the swing timer. If you cast Flash of Light, while the spell is casting you do not swing, and as soon as the spell completes your swing starts counting down from the maximum (3 seconds in our example).

2. Mostly N/A since swing timer does not reset. However, if your multiple targets die quickly it is still a net loss. The length you spend ramping up Censure on multiple targets is a loss of DPS compared to whacking on a single target that already has 5 stacks. You must have all targets running at 5 stacks for a relatively long period. This is something like 20-30 seconds at 5 stacks if I remember the last time we crunched the numbers. Add in the 10ish seconds to stack and you need adds that survive 30-40 seconds to break even - longer to see a net benefit.