DA INQ combat can be a lot of fun if you play on the right settings.
A patch added new challenge options, sort of like XCOM settings, that do things like make Potions heal only 1 HP, make enemies spam abilities, etc.
A shield wall spamming generic templar on the highest difficulty in just the Hinterlands can take 3-4 minutes to kill if you don't use a counter (e.g. backstab).
On default settings, combat is pretty easy and even spammy. Especially if you 'overlevel.'
Highly recommend either going into areas underleveled or playing on 'challenging' settings because the game actually does have a lot of great abilities/counters/combos/breakers -- it's just the default settings of the game make 'em pointless and the 'pause cam' is kinda.... crap. But the mechanics are there.
In terms of story.... I dunno, I liked the plot of DA INQ and it had a lot better character conversation. It had really great secondary characers. Coming form Witcher 3, you'll probably greatly appreciate the increased agency. Especially if you research the past DA stories, and spend a few hours on DA Keep 'customizing' your backstory (highly highly recommend this). The 'stage' for the DA INQ is really great. The weakest part is some of the storytelling and pacing, and I think Witcher 3 delivers much better in that regard (though it has its own sidequest/pacing issues). It's just kinda a more grand story. I dunno. They're... different. Witcher 3 has much better 'acted' scenes and characters, but I really found the machinations and motivations of DA INQ really interesting.
It can be rather diverse, too. Which is a positive and negative. On one hand, DA INQ really explores a lot of different races, sexuality, geography, etc. It has a ton of themes. Witcher 3 mostly just has one or two. But it does those far better than anything in DAI. So, coming from W3, you'll probably at first think... wow, the story has a lot of diversity... there are so many different areas. But then you'll probably feel like, none of the factions remotely compare to Redania and none of these locations remotely compare to Skellige or Novigrad.
So, in that regard, DA INQ is still good but different, which you may find refreshing.
For what it's worth, both games were probably my #2 favorite game for their respective year and I put about... 210 hours into my main DA INQ file, and I think W3 is about 150 hours so far and another 30 in a NewGame+. And I'm pretty biased to high fantasy with politics, and highly highly biased to any sort of 'castle building,' resource gathering, army/base theme game.