Yes storage blessing is actually very useful and very cheap for what it is. You usually get 5 metal from a single gold mine and leather is plentiful with deers and boars, not counting looting. That's the first thing I put back after checking my defense log.
Regarding vault, it is really useless for me now. I have had 300k gold in there for like 3 weeks and don't need to take it out. I'm even thinking of just not using it at all. I have never found myself in a situation where I am short of 300k for what I want to do. But it also depends on your league bonus I guess. At the moment, I get 150k of each resource in empire 1 so that's just 2 victories. The vault may be useful when you have issues saving (e.g. when playing in raider's territory at lower medal range).
Storage blessing should be on all the time I would say, quite cheap for what it is. Forget about the vault, especially upgrading it