Terminus siphon annoying you? You can ult him, which gets rid of his siphon and have your team burst him from there. Your gourd is on the ground, which damages him even if he has his siphon up.
Mal'Damba counters Skye. His gourd can reveal her through his tick damage, he can immune her entire ult and poison damage, and she has no defense to his ult.
Overall, Skye counters Io. Skye does too much damage to Io and Io doesn't have a good escape or anything that can cleanse Skye's poison. Though when Skye tries to ult the point, you can ult as well to immune the damage. That's about it though.