Discipline mechanics have changed. A lot. More than a lot. They've been completely re-worked. Taking a look at your abilities:
Evangelism (Stacks 5 times from your main damaging abilities)
Increases the damage done by your Smite and Holy Fire spells by 4% and reduces the mana cost of those spells by 6%.
Remember Penance is channeled and Holy Fire can be instant cast via glyph.
When you deal damage with Smite, Holy Fire, and Penance, you instantly heal a nearby low health friendly target within 15 yards from the enemy target for 100% of the damage dealt.
You deal damage to heal people. Mind you, this isn't a whole lot of damage, nor is it a whole lot of healing. But that healing gets better with stacks of Evangelism, and so does the cost of those spells. You're now working at a much higher efficiency. And to boot, these spells are a lot faster than any of your heal spells except flash heal. Not to mention, they automatically target those with the lowest HP so you don't have to.
Okay, so that saves mana and keeps you busy doing dps and healing. What about heavier healing?
Consumes your Evangelism, increasing your healing done by 5% for each Evangelism consumed for 18 sec.
Now you're getting 25% extra healing all around, plus you can quickly get 5 more stacks of Evangelism.
Well okay. But that doesn't say anything about shielding... you know the thing our mastery works off of....
Shield hasn't changed. But it is expensive. Keep it on the tank. And use it for emergencies. Otherwise it costs to much. And you know what that means? It's kindof a back-burner spell for us. So don't stack mastery anymore. Your points would be better spent in haste and crit (like the good ol' days).
Give it a try. What's there to lose? Some gold?