I'm pretty sure you can't roll Lifebloom with your original +healing.
Actually you used to be able to but they nerfed it
And that is an entirely different case - since it is the stacking that made that the case. If you cast one lifebloom and half way through your trinket ran out then it would retain it's healing throughout UNTIL you over wrote it with a new cast.
It's nether a buff nor nerf to allow dots to gain temp +spellpower while they are ticking... if you cast the dot with the temp spellpower buff you get the same effect. In the case of being able to refresh SW:P it's a buff because we can have the temp spellpower affect the dot for the duration of the encounter.
My orginal point is that spriests are going to have to re-evaluate taking max points in shadowweaving and their early spell rotation. I'm now thinking of casting MF twice, then VT, SW:P, DP, MB, SW, MF... give me max stacks as MF is applying a shadowweaving buff every tick, I have 6 chances to crit which will occur more often than not procing imp spirit tap, meaning my dots go on with max spell power, plus any on use trinkets.