The healer's job is to be aware of where his teammates are, the healer suppose to follow his teammates closely...
Yes, I agree,... but the problem is when they split up where you can't have them all active on your health bar to heal them. Just today I did the new Mazz dungeon and each person literally was in each corner of the area (the acid pool part) and I couldn't heal,.. i had to choose one...then after we wiped I said "guys, we need to stick together more, i can't heal you when you run off" then we all stayed relatively close to each other (meaning BoL was cast-able on everyone) and we beat that boss rather quickly.