It's not in my interest to bring this up, but as a thought:
Snipe is the only ability I can think of that can kill from across a map without warning. Maybe the target DG should see a bullseye icon in his UI or there should be a visible bullseye over his DG for the time it takes for Snipe to channel. It's not much, but it might be enough for a good player to pop health or for an allied Oak to hit him with shield.
Thoughts? Anything else this should apply to?