Skye and here's why
Skye can initiate both T and CT side fights easily in every area of any maps :
Her dog can gather information, preventing someone from hard peeking, camping a position, can be used as shield/distraction to rush a site, to fake a push on a site.
Not only that, you can time her flashes to flash one/multiple enemies, to fake flash and surprise your enemies (although in low Elo people don't look away from the flash that often I think?). Her flash can also be used to late flash, or just to get information about an enemy and even just to prevent someone from hard peeking you.
Skye can heal. Her ability allow her to heal multiple teammates at the same time, you can stop the heal and heal again after a fight, thing that u can't do with Sage (if you take damage while you're being healed from Sage's orb, it cancels the heal)
Even if Sage's heal is more useful for long rounds, we have to remember that Skye was not made to be a support in the first place.
Skye can cancel flanks and hard push. Her ult is currently imo one of the most broken ones insofar as you can have it for only 6 points. You win pistols, 2nd round, you take one orb every round, you can have easily 3x times your ult a half.