Jadeja is a better spinner overseas. Does the containing job better than Ashwin, adds more value in the field (got enough decent slip fielders already).
Binny at 8 is quite a luxury; he's definitely good enough to bat as high as 6. Good enough to be above Jadeja IMO, but putting a man with two Ranji triple tons at 8 is perhaps a bit disrespectful.
I think part of the reason why Binny was underbowled is that the opportunity to bowl him never arrived. The new ball bowlers did well, and then Binny got the ball before lunch to bowl around the 40 over mark when the ball wasn't doing anything. Then that post-lunch spell by Ishant probably pushed Dhoni into bowling his strike bowlers more when ideally he'd have turned to Binny and rested the main quicks.
By Tea England were 205/7 with 17 overs to the new ball. Bowling Binny then would look defensive. Dhoni was trying to captain aggressively. So instead of using Binny to fill in overs till the new ball, he attacked right away.
Then the new ball became due, and Binny wasn't going to suddenly get the new ball. Then Anderson and Root happened, and turning to Binny with just 1 wicket to get would also seem like taking a step back and making life easy for England. Finally Binny got the ball when all the strike bowlers were exhausted.
He will probably bowl more at Lords.