I found that out very early on, Erlo
When you're in a full raid and fighting starts, it becomes a bit academic which group you're in anyway so I heal whoever needs a heal and is in range.
I do, however, keep my own group's stats bars nearest the middle of the screen so they're easier to keep an eye on, with all other stats bars towards the edge - I owe them that, at least! (Especially if the Raid leader is in your group
). And I also try to look out for the other minstrel's stats bars too.
If some-one screams "heal me", of course I willl try but :
a) I need to be able to SEE them as well as hear them so they need to be in range or try to get in range. In other words, take note of what's been said in other threads and don't go running off after creeps 'cos I sure as hell ain't gonna follow and leave the safety of the main raid!
b) Shouting "heal me" might not be enough for me to spot which of the 24 icons just spoke, even with the red indicator coming on briefly - Now if you shout "heal Fred" you stand more of a chance!
This is what I have learned so far in my first 3 trips to the Moors with Frontline!