Well, it depends on the type attack you are talking about.
If it is a Tournament attack (from the main interface button), then the levels are not taken into account, only the Rating in the Ranking but when you lose you only lose Rating points.. .
If it is a Pillage attack (when somebody attacks you in a dangerous zone), then there is a range of levels within which players are allowed to attack each other (the system will not allow attacks outside this range). If you are attacked and you lose in a dangerous zone, you will be teleported to a city, where you are safe.. So the only way to be attacked many times one after another is if the attacker lost the battle, healed himself and tried again.. (or you have returned to the zone right away after you lost and the attacker was still there waiting, which seems unlikely)
I hope this was useful answer.