Which elite level CHFs of recent times have waited until they were over 28 to become 'champions'? Most of them are nearing the end of their peak by that time.
As has been noted numerous times here, all truly good KPFs have shown promise early on, and become champions well before 28. Brown, Riewoldt, Franklin, Llyod, Carey etc. were all recognised as being amongst the very best of the competition by the erly 20s. Schwarz, as a Melbourne comparison, was ready to join such ranks at 22. 'Good' KPFs might take until their late 20s to make the most of their talents, but elite ones do it early.
Your note about where Jack's AFL output is compared to other top level KPFs is true, and your call for paitence is sensible. However the idea that we shouldn't expect much from Jack in the near future is off the mark. If he's to become A grade, and we need him to and expect him to, he should be showing signs of what he is capable of towards the end of this year and in 2011. If he's to become what we want, he should be amongst the competition's best by 2013.
From what I've seen of him, I'm confident he will do that, but if we are waiting until his late 20s, he will not have been the player we needed.
Given this is essentially his first year, it's not too much of a worry yet - but if he is still only producing similar performances in the VFL by the end of the year it will be concerning.