I think, mental toughness is a misleading word - rather I say PAK batsmen can't react to the situational demands. And, this is purely self made, rather than genetics or mental weakness. If I exclude corruption from my discussion, I can explain that in 3 perspectives - how a batsman or a batting line-up reacts to a given situation?
1. Whenever a team (batting line-up) is put under pressure, or a difficult situation, or simply chasing a target (be batting first or 2nd, doesn't matter - even batting first one has to chase a target) first thing you need is bating skills - that's pure shot making ability, punishing bad balls, selectively avoiding risky shots or fatal mistakes and most importantly all-round game to maneuver balls around, so that score board can be kept active even with 2 new batsmen in or against very tight bowling/fielding. This is first failure of PAK batting - extremely limited batsmen whose scoring areas can be blocked and scorecard stagnates to create a panic : result, desperate release shot.
2. Getting out of tough situations, or reacting to a situation can't be done on theory - that's one can explain a chase with lap tops, charts, plots ... but players has to execute that on field. Now, that execution tactics is mostly dependent on how players are groomed - in the domestic games that they play, how much it's stressing the players, given different propositions - sometimes scoreboard pressure, sometimes time/rate pressure or sometimes simply game skill - say, an opener has to see out Styen's 7 overs opening spell ....... . This is one area PAK players are extremely limited - hardly any domestic game (both FC & List A) ends in nail biters, neither the game is expanded enough to bring different situations in a game. Keeping cool head under a given situation isn't natural quality or someone is born with - there can be individuals (from every nation), who by nature can keep calm under pressure, but they are rare; most players are groomed into a process that reacts appropriately under pressure.
3. Versatility - cricket is an unique game that's vastly dependent on wicket. We consider wicket (or playing surface) only as a factor of bowling, but it's not. There is a BIG factor of being in "comfort zone" for a batsman as well. The more players (batsmen) play on different/diversified surface, they get accustomed to the diversity, can react better, can apply better and most importantly can adopt better. Strategy & planning has a big part in batting, more so on how to approach a difficult situation (or target). Unfortunately, PAK batsmen play most of their games on 2 very much identical type of wicket - either at home wickets in domestics or in UAE, which doesn't prepare them, and PAK doesn't tour much either, plays Test/FC games even less - now it's 2 Tests, in future it might come to 1/0.
Coming to the validation for three points, I can give examples of batsmen between 70s to 90s - some of the best players/batsmen under intense pressure came from PAK, and that's certainly not because of genetics. Even in very early days, Hanif was an outstanding pressure player. Reason I have mentioned many times - most PAK top batsmen of that era was County players, where they played regularly against versatile attack on diverse County wickets/weather and often those games were hard fought, close games - played full distance to the end, which prepared them mentally, but more importantly tactically & technically. Javed hit a last ball SIX, not because he had talent only, but his entire plan was to face the last ball (got Wasim run-out on penultimate ball to be on strike), and he correctly predicted the ball Sharma was going to attempt, finally he had the skills to execute the perfect shot............ on contrary, Mohammah Hafeez tried a scoop against Munaf Patel, when the game was in PAK's favor, or at worst even keel!!!!!!
For the 3rd point, I actually can justify from recent examples. In recent times two of the best chases in Test I have seen in against SRL, once in UAE & once in SRL - both times, PAK batsmen were in comfort zone, against known/preferred type of wicket & friendly attack - no way pressure was less there, but they responded, same can be said in 3rd Test against Poms in UAE (2 times) - batsmen crawled back into the game from behind. Similarly, I correctly predicted that ENG (IND as well, a year later) will struggle against PAK at Oval - that's after losing 2 Tests at Manchester & Birmingham by some big margin or after losing to IND by 140+ margin 2 weeks before; because I could see PAK team flourishing on that Oval wicket - both with bat & ball once team is settled, which unfortunately is 180 degree opposite from what is there in UAE.
Therefore, I don't think it's an issue of mental weakness, panic or lack of skill, or genetics - Imran was the toughest character I have ever seen on cricket field (Otherwise he won't have made such comeback from that sort of injury at that age); rather players are not developed properly to react under pressure and it won't improve unless QeA style asks batsmen to bat out 3rd/4th innings for a meaningful cause - these 250 overs FC jokes on those soggy wickets actually hinder the mental development, rather than developing it.
