Are epic cards worth to max?

So i maxed all common and rare cards, which feels really good, and i have all epics on 5Stars. However it feels like a waste of gems to max out those, since the only card helping me in my farm runs would be WA, and the others seem not to be that usefull (except for tournie) Or am I missing somethi g there? I haven't really bought any modules yet (have legendary + without unique effects) and it feels like it would spike me more investing in these..

Currently farming T7 W7200 Tournie: Champ rank 20-16

Thanks in advance :)