It seems set up to be a world in which stories happen, rather than a game driven by a single narrative, with all the benefit to brings for DLC expansion and ultimately Grim Dawn 2 if Crate chooses to make it. And truth be told, I'm not sure you're even going to experience the end in Grim Dawn. It was a thing even before the advent of DLC, when we used to have real expansions. I'd say you're a little late about episodic storytelling considering Diablo 2 did it over twenty years ago and it's been a thing in every ARPG I've played. Also Grim Dawn feels like it has more quests and owed to the devotion shrines there's a reason beyond mere curiosity to check out caves and dungeons on first playthrough, so you are definitely led to take more of the world in and spend that extra time. Grim Dawn is probably larger because it has two DLC expansions while the original Titan Quest only got Immortal Throne. Not sure if the map is actually larger than that of Titan Quest. I've tried other stuff as well, but that's more in the way back when and with years of balance patches and the expansions I don't even know if they'd play the same these days. Otherwise it's a pretty hands on melee damage dealer. The other one combined the Oathkeeper with the Demolitionist for maximum flamey death, also using the guardians and a fair amount of health regeneration since the Demolitionist has an aura to help with that. Upside is that the guardians cannot be destroyed, so you'll always have at least two pets to protect you from tough enemies while you re-summon your stuff.
Biggest downside here is that skeletons aren't very tanky and you have to constantly summon new ones in combat. It's nice if you want to sit back and let others do the work, to a degree anyway. The guardians have the poison morph to go better with the Necromancer abilities. I combined that with high health regeneration so I can stick around my my zoo does the work for me. That's two Guardians of Empyrion from the former and maximum skeletons and the zombie golem thing from the latter, with a relic that summons a bone construct as well. The latest one is combined with Necromancer for maximum menagerie. My most recent two characters build on the Oathkeeper (since the class was new at the time).