It definitely changes the balance when they start adding that DLC, more levels, more items, etc. So you pretty much have to start over if you play a vanilla game through and come back some time later to start the DLC...well, depending on what kind of min/max gearing type of person you are.
With me, I was perfectly happy coming back to W3 about a year? later after all the DLC and newgame+ was out. I just started a new playthrough in newgame+, to make sure I got some proper green sets and nice epic weapon drops or whatever. ...I think I even had a more complete main-game playthrough that time and it was much quicker. (for one thing--I ignored most of the billions of loot drops on the map--for whatever reason, I wasted so much time in that little canoe all over Skellige, just trying to pick those up, lol).
The DLC for W3 is absolutely phenomenal, though.
I think Cyberpunk has a couple of classes and play styles to choose? This would give me more incentive for a 2nd complete playthrough after the game is thoroughly updated.