Keep your healer alive at all costs othervise you won't last long without it.
Use your tank warrior to pick up any incoming threats as soon as possible.
If you can see enemies are about to approach from your healer's location, move her out of danger, and move the tank into position to start soaking up the damage nice and quickly.
The early moments of a fight matter the most.
Don't rush to add a premium party member, as it's simply not necessary in the early days.