User blog comment:AP Sejuani/LYCaN, the Advanced Prototype (COMPLETE RELAUNCH)/@comment-7709681-20141124215716/@comment-7709681-20141125010138

Destruction Q's armor reduction can stack? That may not sound good (Of course, it won't reach 0, but put flat reduction/penetration on the build or the runes and you wlll.)

And for Synthesis' E, there is only single ability in the game that applies On-Hit effects on an AoE (Fiora doesn't count, that's multi-targeted, like Brand's ult.), so it's something already done.