Sorry to return to this but it's a point I've been mulling over. Your more persuasive point IMO is that Harmison's career bowling average excluding Zim/Bang is 33.84 which is certainly high.
As for the increase in his bowling average when you delete 7 Tests, you're on much weaker ground.
You remove 13.5% of Harmison's tests to get a "huuuuuuge" increase of 5 points on his bowling average.
Personally I consider anything involving Bangladesh (and, since April 2003, Zimbabwe) with precisely zero seriousness when I'm considering "international cricket". It just doesn't count AFAIC.
I'm actually surprised that those 7 Tests in early 2004 are as much as 13.5% of his career but even so, this isn't a particularly large proportion. That means that for 86.5% of his career he was utterly hopeless. I'd say that's fairly telling myself.
Do the same to Dominic Cork's record: remove 5 Tests (his first Test and last 4 Tests against relatively weak West Indies batting line-ups) and his average rises by over 6 points from 29.81 to 36.04. Huuuuuuge!
I'm amazed you can consider West Indies' batting, inclusive of the likes of Campbell, Richardson, Hinds, Lara, Chanderpaul, Adams, Jacobs and Sarwan "relatively weak". Cork bowled at worse batting-line-ups in his own career.
You can make a fair case with Cork by taking his first 11 (IIRR) Tests as "Part One" and saying that most of the rest of his career, bar the odd game here and there, was poor, and that's quite true. Cork for most of the time between the Second Test in 1996 and his farewell (with the seventh ball of a seven-ball over - I forget which idiot Umpire was responsible - being edged for four
) in 2002 wasn't all that good a Test bowler. Not much of this, IMO, was his own fault, and I've always said that had the cookie crumbled better for him he could've been an excellent Test bowler, but that doesn't change the way things actually were. And sadly, for most of his career, he wasn't all that good.
But removing West Indies makes little sense, IMO.
You can do similar things with many, many other players but I won't bore you or myself by trying to crunch all the numbers.
Don't see anything wrong with it, personally. Almost no cricket careers of any length involve things staying the same constantly. So for most Test careers, I'm happier breaking down than pretending everything was always the same.