easy way to fix this just make each world level limited.
you have to be a certain level to gain anything from that level.
you jump in a battle and they battle is won... and you a low level get nothing.. no coins...no clothes.... no cards.... not a thing.... and you get no experience.
your not the level to be there sho why should you get any thing.
oh yea if you jump in to a fight you dont draw in a combatant but then again your spells are useless as well.
that should discourage anyone from trying to jump ahead.
I've never had a lower-level join my battle in CL because I tend to keep teleporting turned off/stay in realms that are not crowded. Actually, the biggest problem I've had is when players my own level join my battles and get me wiped out because they didn't have any sort of healing cards or correct shields to aid me with. To players of all levels: Please ask before you join a battle that's in progress.