I played DW on Beta for a long time (basically OU but with all the unreleased mons) and the set I used for a long time back in the Excadrill metagame was a scarf Gothitelle to eliminate threats for my Exca-Terrak core so it could sweep. I would think it's still a very viable set in this metagame.
@ Choice Scarf
Trait: Shadow Tag
EVs: 252 SAtk / 4 SDef / 252 Spd
Timid Nature (+Spd, -Atk) / Modest Nature (+SAtk, -Atk)
- Psychic
- Thunderbolt
- Hidden Power [Ice]
- Energy Ball
Basically this thing removes any threats towards a Terrakion, Landorus, Conkeldurr, etc. sweep bar stuff like Forretress. Psychic is generic STAB for stuff, Thunderbolt hits Skarmory very hard and can revenge Jellicent under half if Modest (under ~40% if Timid). Hidden Power Ice picks off Gliscor, and sometimes other stuff like Landorus and unboosted Salamence/Dragonite. Energy Ball hits mainly Quagsire. The choice of Nature is up to you: Modest hits harder and grabs some nice KOs that Timid does not, such as guaranteed OHKOs on standard Gliscor and a chance at an OHKO on Skarmory after rocks. However, Gothitelle's pitiful Speed stat means that even at max with a Scarf, it only hits 343 Speed, meaning it doesn't get the ability to outspeed and revenge kill Base 108s (Terrakion), Base 110s (Gengar, Lati@s), and Base 115s (Starmie). With a Timid Nature, all the aforementioned 'mons are covered, as well as Base 120s (Dugtrio, Alakazam) and the Base 121 (Tornadus-T). However, there is a noticable lack in power.
The drawback to this set (aside from trying to choose the better Nature for your team) is that it's very easily Pursuit trapped. Gothitelle is already weak to Pursuit, and with it being locked into a move, it's very simple for things like Tyranitar and Scizor to revenge kill it. However, there is a benefit: since this set sees a lot of use alongside Terrakion, it can come in on Tyranitar or Pursuit-locked Scizor with little to fear and set up freely.
I hope you find success with this set in the future.