It´s moveset is boring, it isn´t a dragon movepool, it is a ground type movepool. Dragons learn beams, learn a lot of type attacks. It´s usefulness is (Generic Dragon Attack) Earthquake, a Boosting move and a boring move such as a Fire move or Stone Edge. Any dragon can do that. Dragonite gets a HUGE movepool, and Salamence at least has Hydro Pump, which is a rare move on dragons. They can have lots of Movesets, but Garchomp has just two movesets. Any moveset you create won´t be as good as the SD/DD set, or a Choice set. They will be gimmick.
In my opinion, even I love dragons including Garchomp, this pokemon has a boring movepool, it doesn´t deserve your time trying to find another moveset. Use what has always worked
You apparently know so much about it's movepool but don't know Chomp can't learn DD. Rage harder next time.