We've seen Bloodline all too often as the dominant pick for ADCs, especially in pro, all last year. We're slowing down all the Legend runes' stacking for minion farming vs. champion killing since Bloodline specifically relies on stacking up. And since pros get more of their stacks from farming than kills compared to everyone else, this should be most impactful at that level of play.
ALACRITY, TENACITY, AND BLOODLINE MINION KILLS PER STACK :  ⇒ 25
Lifesteal per stack decreased; max stacks doubled.
The choice between Bloodline and Alacrity isn't all that exciting, with the majority of potential users simply defaulting to Alacrity without much thought. We're shifting Bloodline to be a stronger late game option, adding a new decision point on top of "attack speed or lifesteal?"
LIFESTEAL PER STACK : [0.8%] ⇒ 0.6%
MAX STACKS :  ⇒ 20
MAX LIFESTEAL : [8%] ⇒ 12%
THE IRON PRICE Gain 0.8% life steal for every Legend stack (max 10 stacks)
PRESTIGE Earn progress toward Legend stacks for every champion takedown, epic monster takedown, large monster kill, and minion kill