I've said multiple times before: DT2 members should require to be included by at least 2 different DT1 members (maybe even 3) in addition to having a net positive number of inclusions.
I am agreed with this point. Yes, DT2 members should be included atleast 2 different DT1. The more DT1 will include, the DT2 position will be more stronger but there should be a minimum more than only 1.
It's need because sometime some evil people manually input own id or friend id in trust list to make them a DT2 member.