DCL isn't started, or brought off the bench, to be a "goal threat" - it's to do all the other things that make Marco's system function efficiently. Tosun is, at least to my eye, "just a finisher" - why he made sense to a "lump it forward and see what happens" dinosaur like Allardyce.
That's quite a claim to say our 2nd striker isn't played as a goal threat. Maybe I'm putting too much weight on his choice of picking to be number 9 but he doesn't do that much to justify his inclusion without some significant degree of a goal threat. In fact, in his first start I thought we looked at our best as an attacking unit with Kean in that position vs Wolves.
I think you're being pretty harsh on Tosun personally. In his one game in the league cup he set up Iwobi with a good deal of awareness. He definitely has that aspect to his game too.
That said, I doubt Tosun will be here too much longer.