I hope you leveled them during training event. :)
About your question is there someone that is useful, where and why - Bulwark mostly. He is Void, Defense based champion, he has defense aura (it was 17% or something and for all battles i think), single target damage dealer, can apply [Weaken] debuff (the lesser one), can apply HP Burn and has really good passive, that has chance to extend duration on enemy debuffs for one extra turn when he is hit. That makes him really good for Early/Mid Clan Boss and make him sux everywhere else. He can be good or excellent addition to your team, depends of what you already have. Or may not fit well, it all depends where are you and what you run on CB. Use this info for general purpose and see if he can be of any use to you.
Now, there are couple of things you can do at this point to make some use of that situation about your rares.
Check the Rhazin fusion, get any rare that is part of that fusion and finish them to 4/40. Better do this when there is a training event. If you can fuse some of the epics there, don't do it right away, (unless you really want to use then right away). Wait for summon event to take place (not the Summon Rush, but the other one, that will give you points based on the rarity of the pulled champions). If you don't plan to use them and you can't fuse Rhazin at the moment, there is no point to fuse them outside that Summon Event. At some point you will start to work on those epics (preferably when there is a Training event running) and you will pull Rhazin when there is a Summon Event. You are f2p player as I am, so... "This is the Way".
Do the same for Relic Keeper fusion if you haven't done it already. You will have to do it anyway.
Keep the void rares.
If you have dups rare, one that is already 3/30 and other that is "fresh" and unleveled and they are not part of these permanent fusion, you can do two things.
*You can keep the leveled one and use the other as regular food. It may be taxing to keep leveled rares unused in Vault, especially when you are f2p and relatively early in the game, but this is the only way to give yourself chance to get something from some of the next fusions. It may not be enough for the fusion itself, but you can get good Epic (to answer your question - yes, you can and if you can - you should). When you are not willing to invest money, you have to invest what you have, in this case it will be your time, efforts and in some sense certain inconvenience.
*Or you can keep the fresh one in your Vault and use those already leveled as base for 4^ food. From your current stage perspective this seems better use of that energy already used. I can't get the whole picture where are you in game in term of progress, but seems to me that you really can use that already spent energy to boost our next 6*.
Don't run Mino with random champions unless you are absolutely certain you will use them. This can turn into a big waste of energy if you don't do it right. You don't want to see those red dots all over your roster. :) This is not good. Every red dots means there is a kitty lying dead somewhere.
Keep your wallet safe and you will be fine.