I'm a bit confused here, i've read about 25 vols of the manga and seen all of the original anime but dark and brutal is not how i'd describe HxH at all.
So why would you say it's dark and brutal!? Keep in mind i'm not up to date with the rather boring (at least I think it is) chimera ant arc.
In the context of the world, the happenings in HxH are pretty brutal. There are some evil dudes up in that story yo. In Titan's world, people die and get eaten every. damn. day. It's way more brutal seeing Eren cope with recent revelations, for example, than seeing random dude 93 get torn apart and smeared on a tree. HxH is similar in that it's not about the body count or sick fights, it's about those moments after Gon gets out in the real world where he (and the rest of the cast) meet some terrible circumstances. The tone may lean a tad more towards the light-hearted than Titan does, but it can still hit you in the gut when it needs to.
In
my opinion, Titan hasn't had that many chances yet to really show what it's capable of.
It gets more serious from there on sure but dark and brutal? Especially seeing as Greed Island is right after? Nah.
I should catch up to the manga though (and maybe watch the new anime). Everything before chimera ant is awesome but Chimera ant arc just didn't do much for me so far.
Chimera arc's anime version is quite an obvious shift from the rest of the show. The show is kind of like (in terms of mood) arc 1 light, arc 2 heavy, arc 3 light, arc 4 heavy, and it continues similarly in the manga as well.