Delta's Skymiles don't expire, so you don't HAVE to use them in the next six months if you're worried about expiration dates. If you do a one-way international in Biz, how would you get home? I'd recommend looking at various cities that tend to have competition to Europe, or non-Detla hubs, DFW is a great place to look. You can often find 40-50K rt Economy to Europe if your dates are flexible. Try looking at Orlando or JFK. Use positioning flights to your advantage.

For me, I'd rather get two economy round trips than one DeltaOne trip.

If you wait for the flash sales, you might be able to get a round-trip to Europe in D1. I got one a few years back, ATL-DUB for 99K miles in D1. Or you can look at the Caribbean, a lot of deals down there, and they're often too.

If you have a DL Amex, you can pay with miles. This would make sense if the cash price of the ticket is low and the award ticket cost is high. I've seen some flights to Europe from ATL for $400 cash by 60K in miles. This would only work if the flight is coded and operated by DL.

Best of luck!