@RIOT: how do you weigh which champs "need" a rework/major tuning more?

Like, i just saw Meddler say he agrees Aatrox needs some major work, but that isn't even in the plans right now (or something along those lanes, basically it's a LONG ways out)

Made me wonder how you guys determine which champs to rework first

Like, why does one unplayable champ deserve it over another unplayable?

or why does one "broken" champ deserve it over another "broken" champ?

The skarner rework of the past imo, felt like it was way from right field mainly because he was one of the "newer" champs that needed to be worked on.