I don't have any problems with Batchelor's development, considering that he is still only 21yo.
To be 21yo and have 39 games of footy in 3 seasons as a HBF is a good effort.
Most junior HBFs spend a good 2 or 3 seasons learning their craft in the magoos before they play senior footy, then usually need 50-100 games to show that they have the position nailed.
Batchelor has come as an 18yo into what was a non-existent defence and, at 188cm, had to cope with fast flankers and mobile talls.
He has also shown that he can be a shut-down defender as well as a rebounding one.
And, for a junior, done it well.
In that time, he has built himself up from a starting 78 kg to his current 87 kg.
Unfortunately, this season, he has been bothered by what I believe is a recurring knee injury, and needs to make full recovery before contemplating putting further pressure on it.
The extent of knee damage to one so young is a concern, but he is still a junior, until next year when he moves into the developmental phase, 22-24yo.
Our list is short of running medium HBFs, Batchelor is a good still-junior one, unfortunately currently carrying an injury. I hope it's not too long to see him competing for a senior spot, and racking up his 100th game in the not too distant future.