I worry that surfaces will be trivialized if the source point cost for bless is removed.
The problem right now is that WITH the Source point cost, Bless almost never sees use. Blessed surfaces might as well not exist at all. It's not even useful to clear cursed surfaces because most of the time, they'll just be immediately re-cursed.
Out of combat, the Vaporize + Pressure Spike Combo is better for clearing them.
I am in Act 4 now, and I have used Bless more in dialogue and on burning pigs than I have in combat, and the lack of reliable source refills in Act 3 and 4 means using it just won't happen.