I've got to say, even with my limited time (around 60 hours between two toons) Grim Dawn just feels "right." In a way that D3 did not, although I did spend lots and lots of hours playing, it was just missing some essential factor. I think it might have been the loot, everything was focused entirely on finding the BIS items for each build, everything below the legendary items was complete trash. In Grim Dawn even the random yellow-quality items can be highly useful (so far), as good or better than the greens and blues that are dropping. I also feel like I have a lot more flexibility in the skill choices I make, unlike D3 where you're basically looking at a few cookie-cutter builds for each class that will function well in end-game.
Comparing to TQ/IT I'd say GD definitely has better graphics. TQ was remarkably "flat" feeling to me, like looking at a picture. GD somehow feels like it has more depth to it graphically. Don't get me wrong, TQ was a fantastic game and this in turn makes GD quite good as it is very similar. I love the two-class system, just awesome how you can choose to diversify (or, just focus in one tree if you so desire).