It's hard to rate defense without knowing:
- what is the armory equipment/guard reserve troops you have enabled for defense, and their level.
- what is SC troop content
In this armory era, how you leverage your armory defense equipment/GR troop, and their level, plays a major role in your defense. Match making is another criteria for winning defense, such that if your medal count is high, then your base can be presented to much higher level attackers and your chance of winning is much lower, regardless of how well you design your base as a simple dump of L9 buffed jumps (>10 jumps) can easily and totally destroy your base.
To me, in term of what is important in protecting your base:
SC troops = 30% of defense
armory equipment/GR troops = 30%
turret/shield/traps = 20%
base design layout = 20%
A good defense player will pay attention to all the 4 components.
I think keeping a couple of mortars is actually okay at this level OR lower (not so at L9 and L10). It's only when you have to face many attackers with jump loads then you may have to swap them out. If you still see ground troops swarm, the mortars can be very effective.