Firearms training is not enough. Given where I live, I can legally carry in my house, that's all. Since I spend most of my awake time outside that comfy environment (meaning no gun), I need to study-practice alternative defensive measures plus a good dose of situational awareness.
Assuming, I am armed I still would be studying various alternatives. Why? Simple: there are times when you may not be armed (sporting event, the local pub, your child's school, bank,...). Throw in the nasty surprises life tends to throw you (gun-goes-click, turn-around-BG-already-in bad-breath-range, walking out of a disarmed event,...) and you will need to "create space". Maybe a "martial art" is not necessary but rounding out your defensive abilities by training in the use of hands, feet, OC, sticks, chairs, and cats has a definite place in the preservation of ones hide.