Well a quick status update, I'm about to take on the Onii King. It's actually been pretty smooth sailing so far (only lost one person so far), but there ARE a few changes to my strategy I had to take.
First, when approaching turnips and jars, you have to "poke" them from a distance with your king's scepter to see if there are any UMA hiding in the bunch, as their spring-up animation can kill your townies at this point.
Second, play it very conservatively with the bosses (who seem to have more health than before...). Cow Bones was still a joke, as long as you only bring four grunts (the fifth one tends to lag behind) and you only attack him after his failed charge. Give yourself three seconds and then recall your troops, because the head's shadow doesn't always pop up anymore. It's also not worth risking an attack when he sends his head scurrying about, as your grunts might get caught between the head and your king when you try to recall them.
Yvonne was even easier, now that her poison attack means jack (what, you're going to lower me to one health? Too late!). Just bring five grunts, and wait until either she lifts her head to spit the poison or she jumps straight up and slams down: either of those are your cues to attack en masse.
The Onii King's going to be interesting because of your lack of ammo. I'm thinking of bringing primarily archers, with just two or so grunts to attack the actual king, but I'm not sure yet. I DO know it's going to be tough, as the first time I tried him (on normal) he still almost killed my army.