Brandish I've noticed is indeed only useable by being X meters from an enemy and targeting it, though it DOES NOT give the buff to the enemy, it gets applied onto you. Though I indeed find it rather weird why it has to select an enemy to use + it even pulls said enemy without doing any damage, I wonder if this is an agro pull ability too?
And for the abilities that change everytime you switch, you could make a layout for your KNOC, and at most, like really at most, you'll have around 15 hotkeybars, that's 5 more to fill up ;)
so you could put 1h & shield onto hotkeybar X & Y, while 2h onto hotkeybar Z then when you switch, one will become grayed out, the ohter will become available :)
Could also change through layouts... but doing that mid-fight seems not so smart (due to the freeze you experience).