Trinkets should not work. It is a bug. Feel free to let us what ones you find and we'll investigate. ( / )
PvP activities currently reward honor and loot, but are not required to complete the Emissary quests. You can completely avoid them if you aren't interested. ( / ) ( / / / / )
You guys have pretty much figured it out, but, right--the passive damage increase on the artifact should not increase Atonement healing. The traits on the artifact itself should ultimately increase Disc's total healing ability (including both Atonement and non-Atonement) by the same amount as the other healers' artifacts. We do want to figure out how to make this clearer.
Disc should be able get use out of DPS trinkets, but we have to make sure they're not overpowered. For example, they have to add less healing than healing trinkets. Corrupted Starlight as the twin problems of being AoE (which will always risk being overpowered for Atonement purposes) and being an RPPM proc (which results in it adding the same amount of DPS to Disc's low damage as it does to a caster's high damage). We will likely reduce RPPM proc rates for Disc on trinkets like this. ( / ) ( / / / / )
These are still subject to tuning; however, they will likely have some variance in how much damage they do (among other reasons, due to the different durations). ( / )