I find Orks are better equipped than most for dealing with a good DE player. Many of their advantages (charging into CC and ripping the enemy to shreds so there is nothing in range to strike back, the various nasty scary stuff, lots and lots of darklances, etc. etc.), are negated simply by the fact that there are lots and lots of Orks, and sooner or Later we WILL get to strike back.
Good DE players do have a tendency to bring two portals, and when they do bring one they tend to be a bit clever about where and when they deploy them as well.