The bolded thing happened because Strange wasn't concetrated enough and hurt (at least that's explanation i enocuntered since i've never seen the scan). Again it was fraction of power and Agamotto overcame that spell. Plus it could easily be PIS since Dormammu alone is = Agamotto. Anyway that all doens't matter since
Vishanti were unbale to grant him a slightest whisper not to mention power him up. So this feat is > Agamotto's feat. Also how the hell can Oshtur grant someone Cyttorak's powers ?
Not to mention that Vishanti already stated that they don't want to deal with Cyttorak or anything which belongs to him.
it is possible that Dr. Strange was indeed not concentrated.. and him not being able to call forth the aid of the Vishanti in Cyttorak's domain is not that great of a mystery.. if Cyttorak was able to incapacitate Dr. Strange to call forth the Vishanti would be a better feat, but as we all know, he cannot..
and yes, Oshtur did grant Dr. strange the Crimson Bands.. see Doctor Strange II #9..
they said that they want to deal with him, but they did not expressed inferiority.. big differences.. same goes on how the Vishanti expressed no desire to deal with Shuma-Gorath and we all know they possess at-least equal power..
So Oshtur gave him item created by Cyttorak which is totaly =/= than granting him a power of Cyttorak. And with all respect to you (since i really respect you) the rest of your post is just you playing semantics - which goes in fan-fiction region. Facts are different.