Nassar Hussein batted somewhere between 3 and 6 in the order - not uncommon. Sober's batted high in the order, as a bowler he sometimes took the new ball, sometimes bowled first change, bowled orthodox off-spin or chinaman or as a stock bowler tying up an end. Dig out the stats of all his "contemporaries" that had the same role in their team.
But Hussain was a captain and at times was asked to anchor and at times to attack, etc...
... every player has certain circumstances where they play a role, this is no different.
We don't have to dig out for contemporaries in the same "role". We know that Sobers falls short for even the spinners of his time (33, 89)*, and someway short for the pacers of his time (29, 71).
If we consider him primarily a spinner for most his career (which he was), then it makes his record even more worse because for a period between 61-68 (his peak) he was bowling pace and that would help his spin-figures greatly - compared to all the other spinners who only bowled spin - in effect, it would benefit him, not impair him. Yet even though they are reduced/helped, his record is still worse than the average spinner of the time. (34, 92 vs 33, 89)
Your point would be like me saying since Symonds bowled pace, spin and batted at 6 he is better than Keith Miller, and you can't compare Symonds with anyone else because no one else had that "role" in other sides side. Hence, I am right, and there is no way you can prove me wrong.
Or even simpler, you're suggesting that you can't compare a specialist's bowling with an all-rounder's bowling, simply because they have different roles. But you can, if all you're concerned with is their bowling then all that is relevant is their bowling records. Just because one happens to be an all-rounder, does not mean he is going to bowl a style a different way or not try his best to take wickets at lower runs and as fast as possible.
P.S. Sobers didn't bat high in the order, he batted mostly at 6 - which is irrelevant as we are not discussing him as a batsman.
*(avg, SR).