@Riot: Marksmen, increase DPS and nerf burst
Ok, we all know about Vayne and her 2k Tumble crits. However, this is an ongoing issue for most ADCs (barring Jhin and Draven who are supposed to do that). So my suggestion is to outright remove the possibility for archetypal marksmen to be bursty. Revert the 5 AD buff from preseason 5, reduce AD from completed items, change crits to dealing 50% bonus damage from 100% and halve Infinity Edge's crit damage increase as well as most others and guaranteed crits. Then increase the attack speed cap to 3.0, increase AS from items, and give a phage item to classic marksmen for better kiting. Voilà.
