The net result of the removal of DFG and patch 5.2...
...won't be a great loss in viability of assassins. It will be a great increase in viability of sending ADCs to two lanes, and of Karthus and Cass mid. Calling it. Assassins will still be strong since marksmen are overtuned, and assassins stand the best bet of dealing with them. But since assassins can't deal with them as well anymore, marksmen will have more overall power, and start to be picked more for mid/top. Karthus and Cass were both kept in check by being vulnerable to DFG, and other assassins.
their laning is utter garbage and nearly every other class will pubstomp them.
Mages and bruisers will continue not giving a #$%^ because mages are getting buffs and bruisers will still be bruisers.