I see where the OP is coming from in one sense. However, the linear/not-linear format isn't what's important to me so much as the interaction with recurring characters and this is an area where BioWare excels at IMO. The fun in multiple playthroughs for me is not only playing a different character, but assembling different parties and getting their (often very different) reactions as I play through an area, which helps make it 'new' (or at least interesting) again. Unfortunately, in DA:O, the 'beginning' really lacks these lasting characters and, for me, that's what hurts it from my point of view.
In the origins tales, you pretty well leave everyone behind at the end of them (except for the odd 'cameo' that might pop up later) and in Ostagar I have no interest in interacting much with Daveth or Jory after having done the 1st playthrough because I know they're not around for the long haul, which leaves you with only Alistair (even Dog is mostly sidelined in Ostagar/Wilds if have him as a Human Noble) to start building any kind of 'realtionship' with.
So, yes, I too find the whole Ostagar/Wilds area kind of boring after the first part because you're always doing it with the same people with the same reactions and same outcomes. At least with Taris in KOTOR you pick up 6 companions that will be with you for the rest of the game - Carth, Bastila, T3, Mission, Zaalbar and Canderous, and you can mix them up a bit, especially if you leave a lot of the side quests until you have most of the characters assembled.