Go for more, 5% starting rate for them is worth it and you might as well just merge them afterwards or use their skills for inheritance, since they both have some pretty valuable skills.
*stares at Julia's skillset looking for valuables*
The Julia isn't too shabby, her preferred boon might be speed for the +4 but if you can't have that, you might as well make her a dedicated mage/dragon check with G. Tomebreaker.
Without the +Spd boon, her speed stat is kind of a loss anyway to be honest. And even then, it's just to stop her from being doubled by as many things. I think you're fine. You're just a little more committed to using the Green Tomebreaker build of her's.
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