Is 440° F too hot for an oven temperature?
Assuming the packaging means 440°F, no, that's not that insane. Casseroles are heavy, with a lot of liquid, so it takes a lot of heat to heat them up, especially if this is a frozen premade casserole. It is on the high side, so you might want to make sure it's not browning too much on the top (cover with foil to shield if necessary) or burning on the bottom. You can always reduce the heat partway through if you have to; it'll just take longer.