He's below, indeed.
But sometime's he's near skyfather and even sometimes above(rarely).
Why? Because the power he has comes from a power who are as powerful as abstracts.
Strange, is for all intents and purposes as powerful as the name he invokes.
I.E
Beats In-betweener
Punks death. Of course you can't kill death, but you can really mess her shit up.
Drax hit her with his blast as hard as he could, and didn't ruffle her clothes. Strange hit her and it layed her out for a second.
Galactus needs mystic help, he demands help. Strange demands Galactus to meet the ground.