Did some digging - Jadeja's strike rates during his 3 300's - 66, 54 and 83. So he definitely did grind it out on the first two instances. He clearly has the temperament to hold on for long innings. In SAF and NZ, one felt that he was intimidated by the situation of being the last recognized batsman and tried to hit his way out of the situation (almost 'pull'ed it off too). So maybe moving him before MSD might give him a little more confidence.
As a bowler, he is equivalent to Ashwin I would say. 36 wkts in 8 tests is pretty damn good imo. Infact, he might be more effective when it comes to breaking solid partnerships. The 6 wkts he got in SAF, 4 out of his 6 wickets were settles batsmen playing on 50s or 100s. And one of them was Kallis who was in proper blocking mode (115 in 315 balls).
I think if he works really hard he could turn out to be incredibly valuable. He has age by his side too