Always great to see a review from you 
Anyways, I JUST finished the DLC. And let me say... WOW. (I am very easy to impress) I pretty much agree with you on the big points. Some thoughts:
The good:
- absolutely adore dwarves and anything to do with their lore, so I could not have been happier with a dwarf-centric DLC
- you are right that the environments are stupid pretty. As in, they are so pretty they made me stupid - about half a dozen times I nearly made the Quiz-Quiz walk off a ledge because I was too distracted gawking at all the pretty they brought this time around. But this I could apply to all of DAI. At least on my console, it is so gorgeous its heartbreaking.
- darkspawn look and feel great. I remember reading a post by the lead concept artist saying "we wanted to make them feel like something you would get after a contagion, with recognizable features, like those were people before they got infected, but the disease ate away at them so much they look wrong." Paraphrased. They are so successful in that regard. Gods they look creepy. And the ogres - where is your nose WHAT IS WITH YOUR FACE. Awesome.
- The lore - it has been a while since a game made me go "WTF WAS THAT". The Descent did that. Every story beat they introduced only made me more curious (wait, did you just say TITANS? what are these weird dwarves? Oh gods they brought automatic weapons? Does that mean those are a thing now? YOU KNOW WHAT NEVER MIND RUNRUNRUNRUN)
- That ending - makes me wonder, with all the curveballs they have thrown with the DAI DLC, from Hakkon (mage-spirit bonds of the Avvar and breaking thereof) to this (DWARF. MAGE. WHAT.), any future games would have to be nothing but story if this is to be addressed in any way in the future, let alone resolved. This is not a bad thing, but handling a dense and layered story can be a handful as those tend to get out of hand fast.
- did anyone else get a Jules Verne "Journey to the Center of the Earth" vibes from this towards the end, or is my old showing again?
- I actually figured we were inside a titan as soon as we walked into that last lit area and the first things we noticed were (i) there is a distinct rhythmic noise that sounds very much like a hearbeat, and (ii) that blue thing down there looks very much like a heart. OMG ARE WE INSIDE THIS THING.
- The final conversation with Valta, when she started raving about how great she feels, that seemed like a giant big red flag right there. Nobody who is a well person says things like "I never felt better in my life" after being hit with a mysterious force literally nobody knows what it is and displaying powers their kind have been physically unable to harness in all of recorded memory. Next time I meet her, my hand is not coming off my greatsword, is what Im saying.
The not so good:
- I liked the combat well enough, I liked that it kept me on my toes, but at times it just seemed spiteful. Fighting off waves after waves after yet more waves of darkspawn was just awful and annoying even at points. The Emissary Alpha fight has been mentioned a few times, and for a damned good reason. Although I suppose it makes sense story-wise, I cannot have that much of an issue with it, but still - in parts, it was not fun because of that.
- The final boss - this DLC did not need a final boss. I will give the waves of darkspawn a pass because again, lore and story-wise it makes sense and I am fully willing to admit I am not von Clausewitz when it comes to battlefield management. But there is no story reason for a boss battle to even be there, nor for the Quiz-Quiz to charge at it head first without even trying to communicate with it in some way (two words: INSIDE and TITAN - if a semi-sentient creature shows up, wouldnt you, I dont know, have some questions?). The fight itself is broken. It is. It is so badly designed and poorly executed it actually made me angry. I SOLO-ED this damned thing. All my party got slaughtered like idiots the first round of lyrium spikes shooting from the floor because they have zero situational awareness, apparently. All I had to do was run circles around this thing (because its rock tentacle-eye coordination is so poor it cannot hit you unless stand in one place for five hours implying all sorts of unsavory things about its mother and her extended family), waiting for my Earthshaking Strike to recharge, then drop that and watch its health go down like I just dropped it in a vat of acid. After I figured this out, the damned thing didnt touch me ONCE. A boss battle should not be cheated as easily as "have ranged ability, run around and use that with no pressure until enemy status = dead". Or silenced. Considering it is a boss battle, the culmination of this entire DLC, it soured the experience somewhat.
But your 8.5/10 sounds about right overall 