The axing of Mohd Amir is wise decision, but should have been taken earlier. Since his return in 2015, Amir has become a limited over specialist and stock bowler in Test cricket. On field he has been used sparsely in limited over cricket. For instance – the finals @ The Oval of Champions Trophy-2017 he never finished his 10-over quota, and since then captain/coach never gave him full 10-over, viz his last 10 games !!.
Where as in T20 he has used his 4-over quota regularly. Interestingly enough has played more T20 since his return and been very effective!.
On the other than in Test cricket he has bowled more since his return. There is rise in overs/inn – regularly bowling 20 plus(increased to 47 % from 37%) overs since his return in 2016….but there is also rise in wkts/inns…. however his wickets have not come in heaps since his comeback. Only one five wicket haul since his return to Test cricket in 2010.
Perhaps selectors want him to be become a striker bowler in Test cricket( similar to LOI ) than just be a stock bowler. Hence it is a sensible decision to play more 1st class matches, so that he can understand strategy, tactics used in 4 day games…. using both new and old ball.
Below is bowling stats year-wise of 3 format using relevant indicator for my analysis.