This is not the first time that a Pakistani captain has overbowled his spinner. Saqlain was overbowled several times by his captain. The following are the examples just under Wasim Akram:
Brisbane test (1995) vs Australia, Saqlain bowled 44 overs in the 1st inning (Pakistan lost by an inning so there was no 2nd inning).
Sheikhupura test (1996) vs Zimbabwe, Saqlain bowled 37 overs in the 1st inning and 40 overs in the 2nd inning.
Dehli test (1999) vs India, Saqlain bowled 36 overs in the 1st inning and 47 overs in the 2nd inning.
Hobart test (1999) vs Australia, Saqlain bowled 24 overs in the 1st inning and 45 overs in the 2nd inning.
Misbah is not the best captain but the weaknesses which are attributed to him only were found in almost all Pakistani captains.
Factually, you are correct, but it clarifies that you haven't seen any of those matches. Let me explain the context -
1. At Gabba, AUS batted for 11+ hours & PAK went for 4 bowlers strategy. In that innings, other 3 bowlers work-load was Wasim 38, Waquar 30, Md. Akram 33. Also, Saq had to bowl longer, because Md. Akram broke down after Lunch on Day 2, after bowling 33 overs out of 135 or so - after that, Akram had to use Saq from 1 end continuously.
2. In ZIM's 1st innings, again, for a 4 bowler bowler strategy, work load was Wasim 28, Waquar 22, Nazir 24, Saq 37. Then, Wasim batted for 10+ hours for his 257*- he was officially 31 then, eventually his body gave-up & in 2nd innings - he bowled only 5 overs, unfortunately, Shahid Nazir also got injured, hence the work load was distributed like Wasim 5, Waquar 20, Nazir 19, Saq 40, Sohail 11 & Malik 5
3. You are exposing your understanding of Test cricket in IND, where, spinners do bowl 70%+ overs. PAK went to IND with 4 bowlers strategy without taking Sohail, hence the work load was shared by Saq & Mushi (Afridi didn't bowl much in a tight match to the Indian who had their nose ahead after winning the toss on an under-prepared track) - besides, WY got injured in 2nd innings (& missed the 3rd Test). The over counts were - 1st innings Was, Waq 13 each - Saq 36, Mush 26. 2nd Innings Was 21, Waq 12, Saq 46 & Mush 26. In that Test, Saq took 10 wickets & Mushi 4 - probably that justifies why Saq was over-used.
4. At Hobart, most of the time, 2 Lefties batted in 2nd innings & WY got injured - Wasim bowled 18 (he was 35 then & had bowled 20 overs on Day 2), while Sohaib bowled 23. Saq took 6/46 in 24 overs in 1st innings as the Aussies failed to judge his Doosra, he was bowled unchanged from one end. To your surprise, in 2nd innings, Steve also "over-used" Warne for 46 overs.
Test cricket is not only about CricInfo stats - try to explain 160 overs bowled by Yasir in 1st 2 Test against WI with Nawaz (both Test) & Babar playing. Also, in UK, Yasir went for 250 runs at Old Traford for his 60+ overs - that's a bowler killer (or his stats killer) - when ENG reached 400/4 in 1st innings, that Test was gone; Yasir's work load of 54 overs in 10 hours, should have been reduced with Azhar & other bowlers. To Misbah's fortune, Yasir is extremely fit, otherwise, he would have been gone by 2nd Test at Abu Dhabi.
Misbah has absolutely no imagination other than usual "go to guy" - that's one major reason he is a good Captain on under-prepared tracks, where result is a function of 450 overs match duration & good "house keeping" will win the match with better resources & horses for courses (& lots of fortune at the time of Toss as well). And that's not only in his bowling options - without Arthur, Babar would have batted at 6 or won't have played at all, as Misbah won't have altered batting order - never did, when he was ODI Captain. Wasim Akram had many "other issues", which I won't bring here, for this post to remain intact - but those 2 are different Captains by the width of an universe.