Mostly the value of DLC depends on if you're using PC or console, as with PC you can use mods that totally turn your experience, cancel out the bugs, etc. Turning a DLC that wasn't right almost perfect. Because, considering content alone, most DLC are worth the money. It's the annoyances that come with the DLC that mainly makes them bad. For example with Dragonborn you can ride dragons, but to enjoy it and enable it fully, you need a mod called Command Dragon. Then you can fly freely over Skyrim (If you have a fast PC you can raise the dragon speed making it more fun). I for myself bought Dragonborn from the begin, knowing mods would soon come out. I've never regret my decision. The new content alone is far better than Dawnguard, as you get Telvanni, Redoran and Solstheim artwork and atmosphere. You get a big isle named Solstheim. A lot of dragon power extensions. And the realm of Apocrypha, where Hermaeus Mora lives. If you can't use mods your biggest annoyance will be an easy to defeat end enemy and a crippled dragon riding.