...basically sorcery is always bad.
From the Imperial standpoint, assuming that it isn't apotropaism? Yeah, pretty much. Of course, we also get into the territory of a culture seeing something as bad and it actually being bad (in the game context).
But Kage, it becomes quite difficult in my view to have any sort of definition of sorcery in the way you describe it, it just seems to be besluddering slang for psychic use with some common attributes that you don't like, which, in my view, is a bit to open ended a definition. You talk about wards and ritualised psychic activity but what do you propose is the source of those activities' power? Is it the sorcerer's belief that reflect back from the warp or what do you suggest? Can you call all sort of faith based mysticism to be sorcery?
Not sure how to break up that paragraph into chunks, so I've left it as is since I guess that I'm referring to it all.
To explain the "structure" comment, that is not entirely off my making, but rather is based from commentary in the official 40k RPG materials,
e.g. Dark Heresy, Disciples of the Dark Gods and
The Radical's Handbook. Admittedly, I feel those books present a very bland interpretation of sorcery, but there you have it. They also take the approach whereby they are just basically "psyker powers" that get called minor and major "arcana" to make them sound more impressive.
With regards to the
power component of sorcery, as with psyker powers that is quite clear: ultimately it derives from the warp. I don't think that anyone would question that.
Erm, but beyond that, and despite the question marks, I'm not quite sure of your question. The sorcerous ritual shapes the warp, which then has an effect in the matterium.
Is "faith based mysticism" sorcery? Well, it really depends on what you're talking about. On my behalf I consider "faith powers" from the game to be functionally similar to psyker powers but... Well, we begin to get into how it is modeled in a game rather than the philosophy of it all.
Sorry about the rambling response, but not entirely sure where you're coming from or what you were heading towards.
Kage