EA honestly did a lot to drag down DAO. There was the overpowered DLC gear and also just a lot of bad cuts and simplifications that occurred in the last year when EA took over Bioware.
Bioware did that all on their own.
No, the Stone Prisoner shit was definitely an EA move. So was the DLC salesmen. Probably pre-order exclusive items as well. Bioware also suddenly changed the marketing and look of the game after EA took over, to make it edgier. There was also a lot of casualization and dumbing down of the original design vision that happened in the last year. While a good part of it is certainly on Bioware, I suspect there was executive meddling to make the game more "accessible" as well.
I don't think this game could've been significantly better even if they didn't cut corners or introduce op DLC gear (which you can disable anyway). The writing and lack of encounter design, mob variety and build diversity are what drag it down. Those things are mediocre at best from the very beginning, so it's not about budget or cut corners.
Encounter design I'd certainly fault Bioware for. But the writing was not so mediocre from the start. Originally it was planned out that Cailan was frankly conducting an affair and planning to divorce his wife Anora (who was yet to bear him a child) in favor of Empress Celene of Orlais, with Arl Eamon (who never approved of Loghain or his daughter as proper nobles, since Loghain came from peasant roots) being the intermediary for Cailan and Celene's affair who encouraged Cailan to set aside Anora for Celene. And marrying Celene would only have given Orlais Fereldan back by marriage after a hard-won rebellion to regain their freedom. Loghain found out about this, and this is what caused him to have to kill Cailan and probably contributed to his motives for poisoning Eamon. This entire angle got cut and it dragged down the story with it, making Loghain into a retarded backstabbing power-hungry and paranoid villain with a terrible sense of timing. Dalish Elves vs Werewolves was originally also intended to be handled in a less hamfisted way, where you don't get autopiloted to the ideal solution (they had to dumb that one down, you see) but instead get two different sides of the story, with heavy grudges and a choice between them, and need to find the ideal solution (lifting the curse) yourself. Dwarf Noble was blatantly intended to have a follow-up route in the Orzammar main quest, but they completely gutted it because it would be unfair to non-DN origins... Oh and originally you would've had to choose between Arl Eamon and the Cult of Andraste for your army, but instead now you get to cure Arl Eamon no matter what. And originally you were going to recruit your party members into the grey wardens and darkspawn corruption (as well as lyrium poisoning) were going to be mechanics. Persuasion and Intimidation used to be separate skills too, in the demo the year before DAO came out (back then Rogues had access to the shield & sword and two-handed weapon talent lines too). There has
definitely been a push to make DAO more casual in the last year before release. And we know EA was responsible for DAO's sudden rebranding and DLC practices. I think a lot of the shit that went south was indeed on Bioware, but EA also played a considerable role in dragging down the game to mediocrity.
The least they could've done is expand the specializations to affect how a character plays, i.e. more specializations like the Arcane Warrior, which I find the most successful out of all of them. I feel DA:O is lacking in effort in pretty much everything except map design and world building, and maybe companions (in terms of content and banter) but they suffer from the overall Disney-esque approach to the writing.
Arcane Warrior was pretty shit though. It had zero offensive moves and was nothing but a spellcaster running around in a giant suit of armor. The NPC Arcane Warriors typically have some Warrior talents to go along with them, but not the player characters. Shapeshifter was also handled poorly. You only got 2 or 3 moves in each form and were mostly sitting on your ass not doing shit. They really needed to improve that spec to make it actually feel like a proper shapeshifter. Not a lot of in-world recognition of specializations either, such as if you were a blood mage for instance. There was also a depressing lack of spec-specific gear. Arcane Warriors got 1 sword and Templars got some templar armor (where arbitrarily only some of them actually require the specialization) and that was about it. The Arcane Warrior sword also says it can be used to cast spells like a staff, but it doesn't affect Arcane Warrior spellcasting in the slightest. AW was a bad case of cut corners, and there was no good reason why it didn't have access to basic warrior talents like the weapon trees. NPCs get that, but not player characters.
That reminds me, there's a deleted scene where Wynne turns you in to the templars if you are Blood Mage spec, but they cut that scene out because they didn't want to punish you for playing a Blood Mage or shit. They even allowed you to make Wynne herself into a Blood Mage now.