Ladders are fine. People just need to learn to invest couple points in shields and magically those roofmonkeys become free kills. If something, just add upkeep in ladders and more serious kicking and banning for those that delay battle by staying on roof after team-mates are dead.
Roofcampers just have to learn to not play like asshats and get off their roof, if they're the last men of their team. In almost every battle I play I can see that those monkeys are not able to get the message. Removing ladders is the only way to stop the roofcamping madness, cause they just won't learn it.