People and ADCs

For the last couple days I noticed alot of people complaining that ADCs have been doing burst damage and oneshotting assassins but I just can't get it. What assassin kit doesn't give them enough mobility or gap closer to get close to a ADC. What type of bot lane did you have to get the enemy ADC so fed that they can "oneshot". Do you forget we have tanks in the game for a reason? And finally what have you guys been doing all game, ADCs take alot of gold to get in their prime and that gold takes alot of time so unless you guys are just letting a Vayne farm up for 40 minutes without even trying to stop her nobody should be complaining when she comes down and makes you regret leaving her alone to farm.