The +5 magic bonus really comes in handy later in the big boss battle in the Greenwich Village
Also they are one of only 2 romancable party members still to be met so if you want to play the secret ending with the grand duel of Penn Station you probably want to have either them or the sage of Honoken in your party
The +5 magic bonus should probably be nerfed all things considered but it's fun enough and that's all that matter
I think that the dialog tree on that first train quest event with them is the most interesting one due to the way it explores our place in the world, human philosophy and the concept of eternity. But I get how it can turn people off of letting them join the party, but I promise that they are more than a vessel for philosophical discussions. They are a well rounded and deep character with a complex past who has clearly made mistakes but lives with them











