I completely disagree... I think it makes complete sense.
These were once two great and powerful races, that through pride and arrogance reverted back to a child like mentality, ie. (Im better than you are! haha he haha.) Its like Sheridan said they were children in the playground.
So... Its not dumb that they were afraid of being left alone, these were two races that had become accustomed to being the top dogs, demanding obedience of others, and to fighting for complete control among one another for over 2 thousand years. And all of the sudden everything changed for them, they were cast out, no longer important, and were told to leave.
They were afraid of the unknown, that's not dumb, its life. (And we already know the Vorlans didnt react well to change, simply when Kosh was killed in Season3, they weren't use to dieing and now they weren't use to being told what to do.) Change isnt easy for some people no matter how old they are.
So when they asked Lorien to join them, I view it less as a child asking for protection of a parent, and more as an adult realizing their mistake and seeking guidence/therapy so they dont do it again.
As for the dialoge being clunky, I dont really notice. Theres alot to deliver and wrap up so I just give it a pass.