Help me again guys

With the recent nerfs I don't know what to lv up and what to not just last night I made king slayer to 700 lv which asked 15k power stone but now it only takes 3500 and the DMG per sec also decrease and

Slime king got it's ability nerf it doesn't bounce any more like it used to And mighty to only gives 317% boost which was 3k last night what should I upgrade and is worthed only mythical I unlocked is placed on the pic Also what should I enhance now will king slayer still worthed?