I pretty much agree with everything everyone has said. It can be cheap to fly from certain hubs. It usually isn't. From Texas, it is mostly NEVER cheap just to get to whatever hub is having that great European fare, but hopefully it will be better for you from Detroit. I've seen $300 fares to Europe, but it will cost me $500+ to get to that hub.
A few things to consider about your flight - we've had delays on legs of our European flights that have delayed us up to 24 hours after we missed the connecting flight. We've had luggage not make the connecting flight when we did. We've had luggage lost permanently (ds's suitcase is apparently on its own walkabout around France as we speak - we we got home a month ago.) We try to fly direct now as much as is fiscally possible, just to cut down the chances of missing a connecting flight. If you find a great price from a hub, but can't get that airline to get you from Detroit to that hub, you may have to fly on two different tickets. Check your luggage, claim your luggage, stand in checkin and security for the next flight. That takes extra time and is another chance for things to go wrong.
We always fly in a day early to cover the chance of a delay. Best case scenario we have an extra day in a cool European city. Worst case scenario, we miss the city but don't miss the cruise.
$1600 seems a bit high, and I'd wait. Unless you have a large group you are flying with, you can wait until much closer to actually get your tickets, as stressful as that is. (I like to have my ducks in a row ASAP for trips, myself.)