assassins and bruisers won't heal as much as adc with lifesteal
Assassins don't need to heal, they just pop people. Bruisers I expect may start running Mortal Reminder for their third/fourth item.
The change to PD makes it even more of a duelist item, it allows the ADC a little more dueling power while making them have to pick their target in team fights more carefully (remember it only gives you damage reduction against the last champ you hit, and % damage reduction really only becomes effective when you've got some resistances first).
increasing every items cost in the game
Note though, gold generation is going to be at an all time high for every class now. It may even out, I don't know, I've not played enough with the changes to say.
they didn't need random buffs or every classes to be nerfed, they also didn't need +5AD at lvl 1
The champs that got buffed needed something to give them clearer identities or to add more synergy to their kits, this wasn't random, this was work that the champs needed. Also that +5 AD at lvl 1 comes at a cost of AD per lvl, this results in less AD at lvl 18, combo this with lower AD values all around and what do you get?
Some champs got indirectly nerfed by the changes, to say every other class got nerfed though is unfair and is missing so many of the other changes going on.
There is a lot that is going to change, is it going to be perfectly balanced on release? Probably not, PBE only has so many people on it and there's no way to find every possible exploit until it hits live (heck even then we're still learning new ones). Just don't count Riot out and act like everyone just got gutted, that isn't the case, Riot is shaking things up as usual, we've just got to see where things fall and expect they will balance things as they fall.