Landscapes really need a full dynamic range, including shadows. For me, the shadow areas are lacking, making it look unreal. This is another problem with HDR, I find that HDR photos look too surreal. That's fine if it is the look you're looking for, but it isn't something that is desirable in traditional landscape photogprahy. Also, when shooting water, it usually looks better to have some texture in rivers and waterfalls, although the misty look works well for coastal scenes. The textures help to emphasise the movement
For me, Kernuak nailed it all in the above quote. I won't reiterate but completely agree. When you use HDR software it is important to get the right settings so that they don't look so surreal or lack DR in any areas such as highlights, midtones and shadows. There's a lot of good HDR software out there. One I recommend that gives the user complete and total control is by HDRSoft - called Photomatix Pro 4.2. Sure, there are various predefined templates to get you started on the look you are seeking but its important to view those sliders until your end result is more realistic vs. surrealistic. As an example the Blacpoint setting should almost always be reviewed to get more or less of the shadow areas. I hope you are able to revisit that place again (what a perfect place for landscape) and re-attempt your shots now that you've got some additional thoughts in mind. I might lay off the HDR, work with RAW and in Manual mode to get exactly what you want. You can always post process afterward to strengthen the DNR, Sharpenss, etc.