I think it was safe in that they by their own admission went for the more classic DT sound than anything else on most of the record, probably as a result of the divisive reaction to The Astonishing, but it was cool to get something like Viper King as a bonus track. I'd love to see them do a record of mostly short catchy songs like Viper King and Our New World.
D/T to me is an album that shows great progression from the Self-Titled, which was their last album where they showed growth in experimenting and "not playing it safe". Since, The Astonishing was a massive concept, it was not going to be a next step evolution of the Self-Titled. Instead of creating new sounds, and even, experimenting with new sounds and ideas, they used their knowledge to create a concept and used their musical knowledge to create music that would go with that concept.
They could go in with that Idea in mind (short catchy songs), but you may not end up enjoying the end product. That's the risk we take with our expectations for every new album by a band. And why, I don't bother expecting anything. I go based off what they say in the press releases, and still don't expect anything, I can have an idea, but I won't have it in my mind that they will fulfill my expectations, if they do than that is just amazing.
People, right off the bat, hear a band is doing a new album and instantly go to their expectations, or more, the dream album they wish their favorite band would make. "I hope it sounds like this, I hope it's not like this".
Not having any expectations, allows me to enjoy an album by a band, when they "play it safe", or go into the extreme experiment realm and is entirely different than the sound they've come to be known for, I.E. Steven Wilson - The Future Bites, and Pain of Salvation - Panther for experimental, and Transatlantic for the "play it safe", it's sound is still easily recognizable as Transatlantic.