My apologise, I missed the Rain and Totem you mentioned. It does sound better then, continueing in the next paragraph, but that still leaves me wondering what you mean that there is a loss in our current mastery, as I can not read that anywhere. Do you want to reduce the effect of the direct heals as opposed to our current mastery? That would weaken us both in PvE and PvP when it comes to direct heals and not provide the healing when it's needed. Then it sounds more that we go in the way of a druid healer, where we will use Glyph of Riptide and spam heal the raid with riptide (I can even forsee this on 25-man) where we let other heals take care of direct healing.
But to make Healing Rain and our totems stronger, the totems stronger sounds nice, it's a smart heal and it can use some more loving (although I nearly cuddle it to death anyways), but Healing Rain itself I already find really limited, that it has to be on a spot (and with movement fights, that's everything but easy), so a buff to it with mastery? hmm, I'm not really liking the sound of that. We already received a buff on healing rain for aoe stacking and from what I've seen, it has not brought the desired effect that I think they had in mind.
Note that I am all in favour for a change in mastery, but not to the cost that we will be back to the garbage dumps in terms of pvp. Note that we still use totems, earthliving and riptide in pvp and I see no loss so far, only gains.