ISketchManager::AddToDB is ssupposedto be used for exactly your case to make the sketch segments creation view independent. But it doesn't work in this case (I have confirmed this from my end as well). What I assume may be the problem is that CreateTangentArc is actually a wrapper function over the create arc function with 2 tangent relations added. So I can suspect that relations require the correct view orientation. Could you try to add the arc via another method (e.g. ISketchManager::CreateArc).
As I said your macro looks correct to me but I believe you have run into some sort of limitations with this particular API function.
Got it working now using the CreateArc. A bit more work to calculate the center point, not everything I will be doing is a nice right angle.
I will have to look into the API functions guessing there is something in there to help or I will have to brush up on my trig.
Thanks a lot,