this has been mentioned several times throughout the post so i will just say it again. DPS spells, namely the instants are VERY force costly. To 1) waste a global CD to put out a dot so that i can get a little more dmg or a kill assist i sa very large waste of a GCD, 2) the cost of a heal spell vs a dmg spell is about 1:2 ratio i am wasting about double my force power throwing out a dps spell, and at the same time loosing a much more effective healing spell to the GCD again.
In an evenly match team. wasting GCD to get a little bit of dmg out can usually mean that someone on your team is dying, on evenly matched teams unless both teams have 3 healers, this is a very rare occurring thing on my server. I am usually spam healing at least one person to keep the 3 people tearing his face of from succeeding.