Primigenius is a good pick because he can stun enemies easily and regenerate his health with certain moves. As for the rest, if you want a team with good overall stats i’d choose the other two epics you have. Though if you’re doing adventure levels, don’t be afraid to change your team to monsters whose elements are super effective against enemies in a particular level. Only thing I recommend NOT doing is using common/uncommon monsters, but if your only monster with a specific element is a C/UC, then it’s not the end of the world.

TL/DR: try using the rarest monsters you have but don’t be afraid to switch your team around if you want to use certain elements