Jos:
Actually, they have not formally disbanded. Noth the singer, Jorn Lande, and the guitarist, Tore Ostby, participate in numerous projects. However, there is talk of a third album, with drummer John Macaluso (among the most underrated and underappreciated drummers in prog) and an as-yet unnamed bassist (Ostby did most of the bass tracks on the first and second albums.)
Personally, I like Ark as much or more than DT overall. Yes, I think DT's "Scenes" is arguably the greatest prof-metal album ever made, and blows away almost everything else. However, DT is maddeningly inconsistent, and in many cases is little more than "speed metal" (albeit top-of-the-line speed metal) with occasional "progressive" sections. Ark, on the other hand, has a more consistent style, approach and execution. although it is admittedly not as "intense" as DT at DT's strongest.
In my opinion, if Ark does two or three more albums as good as the first two - as consistently good - they will rank higher than DT in my book.
Peace.