Well, I find it irrational to start a flaming post yelling 'DONT DO THAT', but I find that offering alternatives is usually a more reasonable route to go.
Easy fix for Devouring Plague - Make the new changes a glyph! As numerous posts have shown, the overall damage of devouring plague will be going up since it benefits from mastery. However, that is a strictly PvE benefit. With a one-click dispel, healers will likely take the 3-second horrify from VT as opposed to letting their partner get hit with a priest's main burst spell.
A glyph would make both sides happy; PvE and PvP. PvE would still benefit from the increased single target damage, and PvP would still benefit from the burst, but slightly less damage.
As for Halo, I agree, a nerf was needed. I can't tell you how many rogues/druids I've gotten out of stealth via me using halo (on accident, may I add). However, I think there is a middle ground to be sought here. Make Halo only take rogues/druids out of stealth within an x yard range. I think that's reasonable. Priests really have no other way to defend themselves when a rogue is close, except for mind sear which requires you to be close to another teammate/enemy.
TL;DR Make the devouring plague doing its damage evenly through its duration a glyph and make Halo only unstealth rogues/druids within an x yard range.