Its a relic from 1.0 OP. Its something that, as it stands is detrimental in the long haul to new jobs being released. It strangles new jobs to be a part of the crossclasses it needs to function, and hurts the fact that jobs could have more interesting set-ups. Much like your astro example, all TP based DPS classes will be relegated to having Lancer sub simply for Invigorate. Without out that skill, they would be lacking in the longevity of their DPS.

Right now, the problem with changing it is, how do you fix it properly? Its tough to awnser, and I think SE is having the same problem...