The sooner people come out of this misguided notion of PSL being a league with "high bowling quality" and use it to justify the low scores in the tournament, the better. There's no factual basis for that argument because you can't judge a bowler without considering the quality of the batsman facing him and vice versa. A poor bowler will make an average batsman look much better than he is and vice versa. The only decent way to compare bowling attacks is when they all face the same level of competition, i.e., in international cricket. 
And Pakistan ranks as the 7th best bowling attack in the world in the last 2 years in T20 cricket, with only West Indies and Bangladesh below them. 
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If you compare purely the pace attacks of different countries, then West Indies leapfrogs Pakistan to push Pak to 8th place above Bangladesh. 
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It's clear from the stats that Australia have the best pace and overall bowling attack in world cricket in the T20 format. 
I would say the batting talent on display has more to do with the low scores in the PSL than bowling quality. I mean, when you have plodders like Luke Ronchi and Ravi Bopara ruling the batting charts, surely that must send the alarm bells ringing. The other day I think I saw Samit Patel's name in the scorecard, I didn't even know the bloke was still playing cricket. PSL have some good overseas batsmen like Hales, Vince, Banton, Roussow, etc., but it must be remembered that a lot of hitters who make their name in the BBL or the English T20 tournaments tend to struggle in asia against the slow bowlers as they're used to hitting through the line with pace on the ball with minimal feet movement. So it's usually the domestic batters who make or break the batting quality of a T20 tournament as they grow up playing in these conditions against spinners day in day out and at the moment, the young domestic Pak batsmen need to up their game to make consistently high totals in the PSL.