If you have the Focusing Lens legendary, Skye can be countered if you use a Front Line as your meat shield. That Skye has nowhere to teleport; landing all five shots on her will be more devastating than you think.

Press F. You will teleport away and Skye can't catch you.

As with all healers, start with poison bolts so her illusions can't heal her fully. She'll receive 1/2 the healing for 3 seconds.

"Smoke screen" blocks line of sight of Illusions, so they can't heal anyone. You can deny enemy heals for 5 sec, just with one skill. Right timing and "smoke" placement is key issues.