I'm not sure if I understand what you're saying , but I do recognize how useful some rare cards can be to fuse with the epic cards.
Currently I have
Lady Vamp - lvl10 and lvl 4
Police Officer - lvl6 and 3
Proctologist - lvl 6
Thinker - lvl 2
Diamond Ring - lvl 3 and 2
If you use best combo screening, Thinker and Diamond Ring combines better than secretary offensive-wise.
I'm considering that perhaps I could spend viagra points on rare cards as a way to boost the combo cards better rather than beefing up the epic cards. It sucks cause we can't tell exact spec as to what the combo cards will be like until you fuse them in battle :/