Why are skarner and Hecarim being gutted?

Hecarim Base HP reduced to 580 from 599 HP growth reduced to 90 from 95 (Net of 109 HP lost) Warpath (Passive) NO LONGER ignores unit collision. Devastating Charge (E) can now move through units during duration of buff.

Skarner Crystal Spires (Passive) Attack speed bonus lowered to [39-90%] from [43-160%] Impale (R) total AD ratio down to .4 from 1

Meanwhile, I'm seeing Lee and Yasuo in almost every game, haven't seen a Hec or Skarner since the preseason started. And Hecarim losing his ability to ignore unit collision is just like salt in the wound; it makes no sense from a power-perspective, to remove a core, defining part of his kit. I would love some context here, because I just can't wrap my head around why this is happening, especially with Hec; skarner at least has a high(ish)win rate (although cutting more than half of the ratio off his ult seems excessive).