Thanks for your feedback!
You're correct about epic wublins having the same polarities as their common counterparts. However, if an epic wublin's like/dislike hasn't been added to the game yet, it won't affect it. (So since Epic Astropod doesn't exist yet, Common and Rare Astropod will have no effect on Epic Dwumrohl)
As of right now, I didn't intend for the greyed out buttons to do anything. This seems to be a bug leftover from when I copied the epic buttons from the rares. It's something I'll fix when I release the next update. (likely later today or tomorrow, since they just added new epic wublins)
I will consider adding an overlap detection feature, that sounds like something that will be useful.