Japanese Maples don't like to stay wet (thinking soil here, at least), so do be careful about that. I've rooted a number of different cultivars and promptly killed most of them with my erratic winter watering habits (a tendency to underwater), in bright shade under a vented dome that kept the humidity inside without it being stifling. I never mist mine. I plant them in a sandy loam soil and water by capillary action when I can; that seems to do well (so long as I don't let them dry out for too long). I've heard they do well (even better?) with bottom heat (can root much quicker that way) and long day length (to stimulate new growth), and I know they don't need nodes under the soil to make roots (though you'll want some there later just in case). Definitely it's important to keep them protected from spring winds and summer drought once they finally get moved outside! (I've lost too many to that as well.) Getting a JM all the way from cutting to safely established in the landscape definitely takes dedication.
By the way, professional mist systems I think are usually set to mist for a matter of seconds at a time, rather than a whole minute at a time. So you might relax the misting schedule a bit. That much mist will keep the soil plenty moist enough with the over-drip, so I doubt you'll need to water that separately. Keeping it humid but not constantly saturated (and same for the soil) is what I recommend.
