And both are Action-RPGs no matter how you slice it. Don't make it sound like you can't compare them fairly. The way I see it they both try to do many of the same things including:
1) Extensive emphasis on open-world/area exploration and sense of discovery
2) Choice and consequence through interactive dialogue
3) Character progression and crafting
4) Gathering forces for a pivotal moment in the story
The major aspects where they don't try to do the same thing includes:
1) Trying to contextualize all side-content for some kind of uniform objective (AKA Power and strengthening the Inquisition)
2) Use of methodical/strategic combat
3) Emphasis on player agency
I find that, in most of the areas in which DA:I mirrors Witcher 3, Witcher 3 just blows it out of the water. I think character progression and crafting is tied but the rest I feel Witcher does much, much better.
1. Mostly just empty stuff in the DA:I areas. Mindless fetch chores and no real quests. In The Witcher almost every side quest has an extensive story to it, and several outcomes.
2. DA:I may have choice, but it has almost no concequence. None of your choices ever impact the Inquisition, or yourself, in any negative way. You get zero setbacks from poor choices, and none of the quests are made more difficult because of a poor previous choice. I the witcher you have pretty severe outcomes for a lot of the choices, and you can even screw up other quests that way. Choices can bite you in the rear later on too.
3. Yup. But no point in it in DA:I since the Barrier spell is all you need. The rest is just an illusion. In the Witcher it is vital.
4. Where do we need these forces in DA:I, exactly? I never saw my army at the end of the game. Couldn't use them for anything but text based missions on the War Table.
The Witcher blows DA:I way out of the water, yes. You are spot on. Both are action rpgs as well, but I think The Witcher feels more like a roleplaying game (outside of combat) than DA:I does. Way more focus on choices and effects of each choice.
I didn't think DA:I was a terrible game, but Bioware do need to improve their act rather severely if they want to have any hope of keeping up. Stop holding the player's hand all through the game, and stop assuming the player has never played an rpg before. You are making an rpg, for crying out loud. Fans of the genre will buy it, and they aren't afraid of spending time learning the game. Nor are they afraid of failing here and there either.