I think what is particularly problematic about disfellowshipping is that the congregation are told nothing more than that a particular person is no longer a JW. They are told not to ask questions about the offence as the person was not disfellowshiped for wrongdoing they were df'd because they were not repentant. Gossip is discouraged and if JCs are held correctly no one other than those directly involved would ever know anything. In addition if an axe weilding, drug dealing, sexual predator elder with murderous tendancies was sorry then it would be kept secret.
This makes Df'ng a blunt tool. Sometimes as in the case of Paulapollos the congregation is deliberately misled into thinking the DF'g was a result of something other than the original offence. So very often even if someone was DF'd for a serious offence how can the congregation protect itself? If you aren't involved directly how will you know someone is a paedophile, drug dealer, or whatever? A few years back a brother sat at the back along side my young family at every meeting, months later I finally discovered he was being investigated for abusing his step daughter. No one took the time to warn me it's all secret. He was finally DF'd but if the 2 witness rule was not met he may only have been reproved and I would still have been none the wiser.
Because of the whole secrecy thing DFing does not protect the congregation at all. Also because of the wide range of offences smoking, buying a lottery ticket, celebrating wordly holidays, immorality, drunkeness, drug dealing, questioning the organisation etc there is no real way to determine who is a more immediate threat and who isn't.
Everyone is lumped together and if someone is reinstated no one questions the past letting potential wolves start again in fresh congregations.
The best way to protect the congregation is to skip the kangaroo court and seek remedy through the legal system, if someone is in prison and convicted in court then that is better protection. There is no secrecy since everyone knows what they did wrong and even if they are released later people know and can make their own judgements.