He is PAK's best fast bowler by some margin. Problem is, he plays for a team which is decent at T20, poor in Test & pathetic in ODI. Hence, his efforts are gone begging in other 2 formats.
Cricket is an unique team game where individuals can carry a team to a certain extent, but other players have to contribute, it's like Basketball to some extent - this year Anthony Davis & Lebron James will miss play off, but will contest for regular season MVP!!!!!
I wrote it probably a year back - what Amir is doing in ODI is more than enough for a good team. But, problem is, other teams don't open with a hack whose every shot is associated with some risk or a stone waller who'll comfortably reach double digit by entire Power Play. So, whatever Amir does in ODI actually goes begging from other end (often), and eventually he is forced to extract something extra, which often will go for punishment. In modern ODI, barring PAK, most teams play their best shot makers in 1-2-3, therefore 5-1-18-0 in Power play should be like gold, unless other end goes for 5-0-35-1 .... net, net every team'll take 55/1 after 10 overs and their middle order isn't bankrupt like Hafeez, Malik, Sarfraz - result is most times that 55/1 ends at 302-6, and people curse Amir - why he is not giving an opening spell of 5-1-19-3!!! Indian opening pacer BK is going at 40 average and close to 6 economy, but he is also effective because his other two partners don't loose the plot almost every day. Statistically, Mashrafee has been better than Amir in opening spell (or overall ODI) in last couple of years, because his team executes a plan as an unit - PP believes in Hollywood spells.
In Test, he was the best fast bowler and MoS for PAK - but, first his team went for 6 batsmen & 3 pacers + Yasir, overloading the fast bowlers .... then batsmen played like tail-enders most times - result is 3 day Test and 3 pacers had to bowl flat out almost every day, defending minuscule totals. PAK's 1st innings highest total was 188 ..... it'll again take Hollywood script to win a Test match from there - SAF isn't ZIM reserves.