I get your frustration from a PvP standpoint, StM is terrible. I'm ok with that though. Not every talent can/should be suited to every scenario. I'm curious do you think MS is worth it in PvP or is LotV still going to reign supreme? I'm leaning LotV personally.
As for PvE StM has it's place in raids and those priests that decide to just pop StM to give themselves a ~2m break are scumbags.