I disagree. While pushing is still the main objective there's still plenty of teamfights to be had especially over the Altars plus you're forgetting that the small size of the map will cause a lot of engagements when people inevitably meet.
I really think that 6v6 Dominion won't be much different than 5v5 just like was the case in SR but in TT your player count is effectively doubled so i'd expect things to be really different.
Not saying there shouldn't be Hexakill Dominion (frankly I was really annoyed that you couldn't Hexakill all the different maps in custom like you could All for One), I just think it'd be better in TT.