That makes no sense, either I'm using cover, or I don't. Mobility doesn't matter then, unless I have trouble getting into cover before the engagement start or when they spawn behind me.
If I peek, I get damage however, that's why you need the regeneration thing by default, or you will be evading shit 24/7 and never fight back and wait for your shields to regenerate. And that's just horrible. You can of course trigger the battle and snipe them from 2 miles away more easily, but that's boring too.
It's also why most people use shield generation and the "generate shield when out of ammo"-thingy on the weapon.