Skittish is stronger imho. Necrotic can atleast be countered by playing correctly. While Skittish is a big "fuck you for playing melee" punch in your face.
Next week is easymode though. Sanguine + Overflowing and Tyrannical. <3
But the week after is like a even bigger "fuck you for playing melee" combo. TEEMING + SKITTISH + FORTIFIED (YOU SERIOUS BLIZZ?)