I used exactly this during leveling and a little more before eventually switching to BoS build.
Its...Ok(In gameplay)...but can be frustrating
Sometimes you will have 5 stacks and no Runic Power to use FoS, meaning you have to use Oblit losing stacks in the process meaning you just lost potential dps.
You also need to use your other spells on the moment you have 5 stacks so you can do max damage before use FoS.