I think Disc and Holy getting Mind Soothe is really good for Disc if it’s even half as good at shroud for enabling skips. I say good for Disc because Mind Soothe along with MD, Purge, DAMAGE, a proper tank DR and group DR and decent mobile healing really gives them a spot in the meta.
Holy lacks the damage and DR and mobility to compete with Disc though.
I think it’s high time for the kings of M+ utility, Resto Druids, to share some of their wealth and for Holy to get a brez. It fits the fantasy of the spec and gives Holy something that Disc doesn’t have which gives a reason for a group to bring a Holy Priest.
Importantly, the M+ meta is going to be even less forgiving in SL than it was in BfA. Holy will be stronger per se but every group is going to want a brez and proper lust which means Rsham and Rdruid are going to be mandatory if groups can’t get a DPS to cover them.
IF Mind Soothe is a replacement for Shroud I could see Holy being popular along with Disc but that’s pretty unlikely. If BDK/Guardian aren’t meta tanks then the meta healer becomes Rdruid unless Lock/DK DPS covers it and Rsham becomes healer due to purge being important in SL but Rshams bring more damage, more throughput, AoE stun, better defensives and better mobility than Priests.