Name me one thing Custom Origin characters get that is unique to them?
I can list several things origin characters gets that custom origin characters do not get.
The XP is pointless to worry about; it might make the game slightly easier but it's not going to make the difference between being level 20 and 60 at the end.
It is the difference between being level 2 and being level 4.
Go ahead and list those things for me, because aside from their personal stories (which includes personal quests) and their unique ability they don't get anything. Also, if you add them to your group you get access to all of those things anyway so you don't have to play as them as your MC.
As for the difference between 2 and 4, that is why I said slightly easier because of the XP give at the start and the initial power spike standard to any cRPG (when you first start getting actual gear and etching out an actual build).
Like I said, you're nitpicking. This might matter more if it was an eSports title or an MMORPG, but it's not. Even if you have to level more slowly, boo hoo, wait for a mod to "fix" that for you or just play the damn game and stop complaining. People have soloed EA on every character archetype, you're going to be just fine.
Somehow thinking custom characters are second class citizens is ridiculous. What are even your solutions to these "problems", you seemed to have ignored that conveniently?