for survival, I guess? Problem with heal is that it can heal two people and provides a short MS boost; it would be unhealthy for it to counter ignite with that level of power. Mages have been taking it as a defensive measure against assassins, don't see why marksman can't.
Usually, as a support main I prefer the bot laner (not just ADC) to take heal, but you can take barrier I guess if survival is more important. I'd probably nab heal (if it's a defensive lane) or ignite (if it's an aggressive lane versus an aggressive lane since they'll likely target you).