Well that's a bit of bull. If each spec is getting the same amount of AP to use when you redeem an AP token then Druids are not getting any bigger benefit then Demon Hunters at all. In fact with the current system Demon Hunters are the class that benefits most from AP gains than any other class considering they only have two specs to dump AP into and they can effectively power up as a defined dual spec character whilst Druids, Monks and Paladins have a harder time powering up as a three role class. If anything a model that shares AP among specs is infinitely more fair than the current system but doesn't fit with Blizzards "it needs to be a bad grind doe" approach.
As for players investing heavily into their specs, well you have people who have the desire to get their weapon done instead of having a half empty bar on their screen and then you have the people who realise that in 7.2 a bunch of new traits are coming and getting your weapon capped before then gives you a definite boost into investing in the new abilities not to mention capping your weapon now gives your spec a definite boost. I don't see how that makes you it should be left per spec. -_-
People are predicting it'll be another 3-4 months before artifact knowledge 40 can be reached and that's if the time to completion for each work order isn't changed before 7.2's release. Add on the fact that the new traits cost scale crazy high and you should be able to see that the AP system is becoming more cancerous.