Yes basic structure not class specifics we should be debating issues we see with things like not having enough panels for multiclass toons that is clearly apparent. Not knowing anything in those trees means saying x+y tree is too strong has no basis.
I am sure devs are aware of some glaring combos like have been mentioned in this thread and in reality they probably already have some built in safeguards from it becoming overpowered.
They seem pretty involved in providing us information early enough on this to give some valuable feedback that could result in changes here and this is a long long project more than 6 months out so theres plenty of time to get into specific combination issues as more info comes out to allow us make a more educated satement of x+y is too good.