Maybe if you tried to have your sub player in the reserve spot too? Just a thought, it may be silly, I've never tried it.IMHO, to get the 36-12 balance of minutes quality matters more than stamina. That's why I said you need a 10 player roster. If your sub is not a scrub it's very likely to be somewhere around there. For my games, rating doesn't reveal everything: As we all know, a player's rating decreases as he spends more time on court. 12.0 for a 9 minute performance compared to 13.0 for a 39 minute performance doesn't mean that players are that close. If the minutes were the other way around the rating would be 10.0 for the sub and 15.0 for the starter.
I don't get the last part. Slow tempo tires players much less than high tempo. Try PTB and you'll see much more subs than Patient or Princeton that you're running lately.