Gameplay changes to expect from the Tier 20 set

[Yunzi]

Subject to change, but currently:

Item - Priest T20 Discipline 2P Bonus (New) The first bolt of light from your Penance deals an additional 200% damage.
Item - Priest T20 Discipline 4P Bonus (New) Power Word: Shield has a 25% chance to cause your next Penance to be free and have 50% reduced cooldown.

Since we're already casting Penance as near as possible to CD, the 2-piece is just a boost to Penance's power and has no gameplay effect. The 4-piece mostly likewise - we're already casting PWS near CD and the additional Penances from the cooldown reduction will mostly replace Smites/empty GCDs.

There's one gameplay change here though in raids, for players who currently don't cast Penance during Rapture - casting Penance during Rapture is greatly boosted in power, so it will now be "required".

This free mana spell will both help the spec become more active (as free mana Penance is used sometimes where an empty 1.33 GCDs used to be) and will reduce the mana required per minute to play Disc (as free mana Penance sometimes replaces Smite).

[Deleted]

The synergy with the legendary belt (and situanionally ring aswell) is pretty legit too.

[Yunzi]

The synergy with the legendary belt (and situanionally ring aswell) is pretty legit too.

It's intuitive to think there's synergy with the belt, because the power of Penance is boosted and the belt increases the frequency of Penance, but the overall effect of the tier bonuses may well be to reduce the value of the belt.

It's really a Smite Belt. It boosts the value of Smite (that it resets Penance). The tier 20 bonuses reduce the number of Smites that are going to be cast, and over 25% (because of Rapture) of all Penances will now have a 4.5 second cooldown instead of the normal 9 seconds, making the Smite belt virtually useless following those penances.

[Flykz]

While i kinda like the 2p, I find the 4p quite sad - it adds more RNG to the spec, when crit is essentially already a lot of RNG and can drastically affect our output during burst phrases. I really like penance, but compared to our current 4p, it's... well, you get it.

Cool stuff for mythics+, though.

[cruxxy]

Holy boni are pretty great. Nothing really fancy but helps holy do what it does best