It seems like in these discussions about aptitudes people ignore the fact that if one character gets something for cheap then something else will be more expensive and will likely more or less balance out. If I buy willpower for 500 and perception for 250 and someone else buys willpower for 250 and perception for 500 we are still on equal grounds. As long as everyone occasionally strays outside the bounds of their class then everyone's xp should stay even and the aptitudes mean that everyone will have something that would be useful that will not be cheap for them.
This is actually a decent point, and you're right that DH2 somewhat de-emphasizes WP for psykers. That said, this critique would hold a lot more water if the aptitude system were actually balanced 1 for 1 like you suggest. As it is, some combinations of starting options yield drastically better aptitude matches than others. You can have a starting character with 4 cheap characteristic advances and a starting character with only 2 and the one with 4 is going to get a lot better at their thing a lot faster than the one with 2.
My real issue is with the aptitude system as a whole. It presents itself as an open character advancement system but is actually a thinly-veiled class system that can be greatly exploited with system mastery or one that can greatly punish the players for making bad choices.
I think the only aptitude that's questionable is Leadership, the others all have broad uses.