I started to lose my sanity at the 7th doctor in 2 days. I'm not saying make it impossible to get a role you already had, but at least put a 10% chance to get a roles you haven't had before. Most leavers leave because they get a role that that they have had about 5 times already. Some leavers are just trolls but that's my 2 cents.
I might be biased from the post-Doctor Stream rage.