Team batting in the 1970s:
As you can see, we're last by some margin.
Team bowling in the 1970s:
As you can see, we're again last by some margin.
Now, if we remove Hadlee's bowling stats from the 1970s:
then as
@Coronis has calculated, the NZ bowling average would go up from 38.95 to 41.21 and we would still be last, by an even bigger margin than before.
Team batting in the 1980s:
You can see that we're fifth, clearly behind Australia and slightly above England.
Team bowling in the 1980s:
You can see that we're second, well behind the WI and a little ahead of Pakistan.
Now, if we remove Hadlee's bowling stats from the 1980s:
then as
@Coronis has calculated, the NZ bowling average would go up from 30.38 to 36.33. This would drop us from second to fifth, slightly ahead of India (36.39).
The assumption which is being made here is that Hadlee's bowling and the other NZers' bowling are independent of each other. This is probably not the case. The presence of a very penetrative bowler like Hadlee would put more pressure on the batsmen and help the other bowlers to take wickets so without Hadlee, the NZ bowling average would probably go up beyond that calculated mathematically, i.e. it would probably now exceed 36.33 and in all likelihood, would now exceed India's of 36.39. Thus our bowling position might well drop to sixth place. Our bowling average may still remain better than SL's of 39.53. Of course, it would also depend on whom they replace Hadlee with but it is unlikely that it would be someone of Hadlee's calibre.
There is another effect of the removal of Hadlee's bowling: the other teams' batsmen would not have to face him and so the batting averages of the other teams would go up slightly. We're currently fifth at 27.82, just ahead of England at 27.71 but with Hadlee gone, England's average would go up a bit and might end up exceeding ours so we might drop to sixth place. Our batting average would probably still remain above SL's of 24.22 (or rather, above what SL's batting average would be elevated to).
The removal of Hadlee's batting would also have an effect but would be less impactful.
So conceivably, without Hadlee in the 1980s, then excluding SL (who did not exist in the 1970s), we might still end up last in both the batting and bowling averages albeit, not as badly as before.