Yes, I'm aware that most supports have damage triggered voicelines to let you know they're under attack, but sometimes it's miniscule garbage like a lingering Moira orb or DVA shooting from full screen. There needs to be a manually triggered button for healers that tells DPS and tanks that they need serious help, and the best thing I could think of is "I NEED PEELING!" since it rhymes with healing and it's an accurate term that high elo players use for protection.
