The best way to keep a party alive in combat is prevent the damage from occurring in the first place. At low level, there are plenty of highly effective ways to prevent enemies from dealing damage. Just from the wiz list, there's create pit to target reflex saves, glitterdust to target will, and stinking cloud to target fort saves. All of those ignore SR too. There's even two sides to this equation; I just showed the debuff end but there's also the party buff end. Wiz have resist energy, protection from energy and stoneskin. Clerics have shield of faith and magic vestments. Druids have barkskin. Those are just the spells that can be applied to other people when you add personal only spells you get to add goodies like mirror image.
As an anecdote, I had an arcanist get to level 12 with extend spell and spell tinkerer casting communal resist energy on the party. Sure that effectively ate all of my level 4 slots but I knew ahead of time that there'd be mostly casters in the tower. Those 5 slots saved hundreds of hit points that any kind of healing would have been unable to match.
There is a pretty basic mismatch between healing and damage. Just compare standard damage spells to the cure spells of the same level.
Level 1: Shocking grasp (3.5/lvl) vs CLW (4.5+1/lvl) tilts to damage at level 2.
Level 2: Scorching ray (3.5/lvl averaged) vs CMW (9+1/lvl) damage ahead at all levels
It only gets worse from there with the excep. Looking at the numbers, it might be reasonable to replace all cure spells with their mythic versions sans the ability damage healing.