"My automaton doesn't ever cast silence on anything unless I signal to it to use enfeebles."

the confusion I think comes from this line. You don't signal it to use enfeebles, the whm head defaults to it, unless you signal for it to start with something else first. But, if you are full hp, or mob is below dc, you really can't do anything but have it cast enfeebles. Its then when you decide what enfeeble to start with first, silence, bio, dia, blind etc.