Yasir still is taking about 5.8 wickets/Test, which is simply phenomenal. What we are saying (about sharing wicket by others) is right, for that Murali has 800 wickets in 133 Tests - that's 6+/Test; and Warne has much lesser - 708 in 145 (4.88/Test). But, I also thought so in straight line, until I noticed another figure - his SR is 57.5, Warne's 57.4 & Murali's 55.0 - which suggests guy individually was as penetrative as Warne, but he had to carry lot more work load than Warne, because of the other bowlers in his team. His other major KPI actually is better than Warne - 13 5fors in 30 Test, vs 37 in 145.
I think for that 3 years, more than Yasir benefiting from PAK's lack of bowling options, it was more of him carrying a below per attack. Before heading to NZ in 2016, in his first 19 Tests, he had 116 wickets at 27, with a SR of 54 & 8/2, 5/10 for. And, during that period he actually played 4 Tests in UK & 8 in UAE, which is probably the worst Asian place for leg spinners. Another of his Test in BD was also played at Khulna, which produces regular scores like 600-6d in our FC cricket (still to anyone's surprise - that West Zone's 1st choice attack when everyone is available should be Mustafiz, Rubel, Mashrafee, Shakib, Miraz & A Razzak - bowling on roads in FC cricket does have an adverse effect I guess

).
Instead of benefiting from lack of partners, I think he has hampered more for it in that period. His long term spin partner Zulfi had an average of 39 & SR of 83, playing entire career in ASIA, which is simply not good enough to support (Add Newaz for 2 more Test, that figure should hit 50/100 I guess

). Regardless of bowling action issues, Ajmal's numbers are outstanding (178 wickets in 35 Tests @ 28/65 stats), but at same time his partner Rehman wasn't a novice either (99 wickets in 22 Tests @ 29/70). These figures suggest that, Yasir actually was hampered by lack of partner than benefiting from it, as teams could have played out him more carefully - had PAK got a strike pacer like Abbas or spin partner of Yasir like Ajmal or Rehman that time, his numbers would have been 10-15% better at least & PAK's record lot better, in terms or runs/wicket or SR, and obviously Test W/L.
Personally, I am a big fan of Yasir, because I like Leggis; and the guy kept PAK relevant among top Test teams for 2-3 years almost single handed. He is struggling now and I don't see him coming back to his best ever again, because of fitness & age. Yasir was introduced too late in Test cricket, at official age of almost 29 with 270+ FC wickets in possession in 12+ years FC career - that's minimum 6 years too late for PAK's standard (FC debut was 2001-02, as a 15 years old baby, Test debut in 2014-15). Ideally, he should have been Ajmal's partner from the day Kaneria got banned (August 2010 was his last Test).
Coming from his doping incidence, I think guy always struggles to manage his body weight, something Warne maintained being caught only once

; but Warne retired at 37, and at Australian 37 - going by Yasir's FC debut, my hunch is he was born as about 5 or 6 years old - which has already taken him past Warne's retirement age; therefore I don't think there is any way back to top. PAK should look to cash in him in Asian condition selectively for at most, couple more years and immediately now MUST start to look for couple of "Officially" U23 leggis, so that after 2019 "home" season, they can replace Yasir.
Looking at his phenomenal record by the official age of 31 or under, I really feel sorry for the guy - should have been standing on like 350 Test wickets by now & prepare to retire in peace. But, this has been the biggest curse of PAK cricket in last 2 decades - PCB is acting like mature cricket board of IND, AUS, SAF & ENG - that's debuting players after almost a decade of FC experience - hence Yasir Shahs, Sohail Khans, Rahat Alis, Wahab Riazs ..... are fading away at the official age when they should be on top of their game. I hope, Abbas proves me wrong - otherwise, his sell by date won't last till next English tour.
[MENTION=132916]Junaids[/MENTION] - as of now, Shadab has no future in Test cricket, until he develops a stock ball, which he can bowl effortlessly on spot for 4-5 times in an over. I am happy that your craze about Nawaz averaging 35 with bat (& 38 with ball) has got cured, and Shadab actually is a better prospect for your formula than Nawaz - still a Leggi MUST make the XI first as bowler - that Yadav (??) experiment by IND at Adelaide ended in tears. Against IRL, PAK would have won regardless of him scoring 50 or duck & same at Lord's; but at Leeds, his 52 didn't do much in a loss by innings & 55 - a better specialist bowler definitely won't have let ENG to get a ~200, 1st innings lead on that wicket - my hunch is PAK would have made ENG bat again, had a 4th pacer played in that Test over Shadab, even after taking out his 56 runs for that Test.
In SAF series, PAK will need a spinner at Newlands, which should again be Yasir or the best leggi in country (If Shadab is the next one, so it be); but for other 2 Tests at Centurion or Wanderers, it's better to play 4 specialist fast bowlers backed by Haris & Azhar & 6 batsmen - if Shadab's 30 & 20 in your formula becomes 20 & 15, PAK'll become a 10 men XI on those 2 venues. For a note - Ajmal was listed to bat at 11, and he did almost won last time at Newlands, taking 10 wickets, before PAK's batsmen & fielders chocking it out.