Well unless you're like 80 years old, I'm not sure how you rated Keith Miller as one of the best captains ever. Surely you're going by what you've read and not what you've seen. You can rate batsmen and bowlers who you've not seen by analyzing match figures but captaincy has to be seen first hand before making a judgment as to how good one was.
In my view, Salim Malik had a very short stint as captain. He was one of the shrewdest at reading the game. Wasim was the alpha male of the 90s and therefore Malik had no chance. Also Malik couldn't secure himself in the team with his batting and that was a huge negative for him. I rate Salim Malik very very highly.
I am well, well short of hitting the mark of 80.
Coming to judging Cricket without watching the game, I think, it's opposite for Captaincy. You can judge a player (without watching) only from stats, which is made against his contemporaries. Therefore, statistically Bradman, Barnes, Laker or Jobbs were outstanding but you can't compare players of different era unless there is standard measuring unit - I can say U Bolt is a better sprinter than Jessi Owens, but can't/shouldn't say that Bradman was a better batsman than Viv or Pele was a better/inferior player than Messi.
But Captaincy is different issue - you can find lots of insights just from Match report, bowling chart, scoring charts (where batsmen have scored), combination used, toss decision, batting order, declaration timing, partnership .... etc. if you really can analyze a detailed scorecard. It's tactics that's are almost universal - in 1932, Jardin was brilliant to chalk out a tactics to negotiate Bradman, or the SAF Captain of 1900s who used 4 spinners to win a Series against ENG, or Len Hutton using Tyson to win an Ashes down under or say Frank Worrell in 1961 AUS tour.
Coming to KR Miller, indeed it's based on reading articles, lots of it - because I haven't seen him even in archives ever leading a side. However, I have read lot about his game intelligence, his versatility as a player, his vision as a leader to promote youngsters, and his capability to raise on occasion - these are universal qualities of a Cricket captain.
Salim Malik indeed was a brilliant captain - much better than his other contemporaries if we are ready to disregard his other issues. At a time PCB's team had about 8-9 past, present or future Captains in playing XI, a number Aussies couldn't beat in almost half a century, and Malik was good. I wrote here sometimes back that if Malik is pardoned, then he should be used as a Junior coach for U16, U19 & A Teams and groom future Captains. He is among the last few PAK players who were groomed by English Counties - from an average FTB between 1982 to 1987, he spent 2-3 years at Essex between 1987-1990 and arguably was among top 2-3 middle orders between 1989 to 1993, and excellent captain as well. Not sure if he qualifies for this list though because he got more than proper chances, but himself blew it.
