User blog comment:CrockamhillDrive/Proposed Xin Zhao Rework/@comment-27332601-20151213204206/@comment-32109419-20151214203819

Getting permanent stats (that stack indefinietly) from an ability is generally unhealthy unless it is on one of these stats:

AP, Armor, MR or HP  (AS but it has a cap, additionally it is unhealthy since it will allow you to build only AD and gain the AS for sustain dmg for free) Mana and Mana Regen (mana and regen might not be good due to the nature of the resource)

Getting another stat like AD, AR (attack range) either penetration stat, MS, HP Regen is just plain unhealthy regardless of how you need to stack it. Because in the end you will be murdering everyone and things like that (Say you somehow get 250% bonus MS nobody can kite you or run)