Rahat is a rhythmic bowler. He has won one Test in UAE.
If you look at his Test stats, 58 wickets in 40 innings, but 8 innings of 3+ wickets - that's 35 of 58 in 8 innings and 23 in 22. This indicates that his range is too wide for up & down - he is not a consistent performer (good/bad isn't a question here). PAK's pace resources doesn't have the luxury to find a pacer who would take 35 in 8 and 55 in other 22 - that's 90 in 30 innings; or 20 Tests. Next best option is to pick someone, who has a spike in performance and hope that out of 4 innings, he has 2 spikes. Besides, guy has majority of his 58 for top 6, instead of doing tail cleaning job.
Coming to his inclusion in Test XI, this is probably the only wise decision among limited pace choices (you don't credit selectors for picking Amir or not dropping Hasan). This PAK attack is vertically challenged - among taller pacers there are only 3 experienced - Rahat, Wahab & Sohail. Sohail is struggling with stamina while Wahab isn't an English condition pacers, though still I would have taken him instead of 9 specialist bats. You need one new ball pacer to partner Amir and based on PSL opening spell, I don't think there is any one remotely close to Rahat.
10 wickets in a game doesn't depend on bowling quality only - Bob Willis doesn't have any, because whenever he got 6+ in 1st innings, somehow he hardly had the chance to bowl in 2nd - 325 wickets in 90 Tests doesn't look anything special, but his average and SR was among contemporary best. PAK domestic had been played for 250-260 overs during most of Rahat's career (probably entire career - I have been complaining for last 7/8 years), often pacers don't get 2nd innings/not needed in 2nd innings to stack up numbers. He has 244 wickets at 24 in 69 games (122 innings) with a SR of 48 and 24 innings of 4+ wickets - more than enough to be one of 5 for this PAK attack.
Admirable to go so far out on a limb for Rahat but, to extend the metaphor, everything in this reasoning creaks mightily. And I say this as someone who always enjoys your postings.
Pakistan's pace options are limited, ie there aren't many suitable candidates, only if the job description is to be Rahat Ali. Only if the intent is to put the fix on the application process would it make sense to insist that only tall bowlers with 'experience' need apply. Criteria which are in and of themselves dubious.
Rahat's is notorious for NOT being a thinking bowler. He is someone who runs in and hopes for the best, and often looses confidence. In other words, 'rythmic bowler' is a euphemism. He is soft, perhaps the softest player to play Test cricket for Pakistan in recent years. In other words, he is a bowler who does not become better with experience.
If the criteria for selection of new Test bowlers extends beyond being Rahat Ali, then
are better options than Rahat Ali. Mir Hamza and Sadaf Hussain.
An inability to take 10 fers is not explained by the peculiarities of Pakistani domestic cricket. Mir has 6 10fers and Sadaf has 5 10fers.
Rahat's domestic average of 24, is merely good by current standards. These days it does NOT by any stretch place him in the top 5 bowlers in the country. Mir and Sadaf average around 19, with SRs around 38. Rahat averages 24, with SR 48.
Every attribute a bowler possesses, be it speed or height, is desirable in so far as it translates into wickets. Comparatively speaking, Rahat is not very good at wicket. This suggests that his height does not afford him the advantages one would hope for.
One bowler who clearly leverages his height to great effect is Sadaf, who is regularly more effective than many faster bowlers. Indeed, Sadaf is the tallest, well performing domestic bowler available in Pakistan, after Irfan. Mir Hamza is just a bit shorter than Wasim, going by pictures, which would be tall enough for many.
No Test bowler should be selected on the basis of performing in a T20 tournament. These are different formats. If we cannot agree on this then we won't agree on much else.
Rahat has an awful record in England, averaging a scarcely believable 50 after three Tests there.