I am not sure assasins will be weak. They have some nice addition in the new mastery, the new corrupting potion will be also strong for some assasins. The new rift herald is also there what can make the game very snowbally ( and take less damage from ranged champions). It's hard to predict how the meta will change. Atm assasins and adcs are not weak. Carrys are insane if they get protection 20% life steal and 1200g qss and lots of, lots of dps how they can be weak? Tanks probaly the only class what is weak atm.