Because they set XP requirements like that, it's not their goal to get to level 250 quickly and easily. The average player is level 180, so it takes about 10 years to reach level 250. They certainly won't double the easy XP because then it would take 5 years to get there, and that's not their goal.
If they drastically increase the XP that can be gained from jobs then those who have a lot of time (and money) will have a big advantage. They would reach level 250 in 5 years, while the average player( who doesnt do 15sec jobs) would only be at level 210. That's too big level difference and many would complain about it. So it is better for them if the active players can progress slowly and are only a few levels ahead of the majority.
What I'm hoping for is that they'll increase the new works XP a bit more (+20%) to really make it feel stronger.
Also they need to save the PVP part of the game. They should double the XP reward for ff and increase the XP reward for duels in comparison The reward for higher level quest should be multiplied.