This looks like an amazing team, I haven't played much DW but Slowbro is great and in OU I loved using Air Balloon double dance Terrakion back in the day. I really like the role you've given Garchomp too, the offensive synergy with Terrakion looks perfect. I may just give DW a go with this team!
One thing about your Slowbro, why those EVs? I would have thought something like 248 HP / 216 Def / 40 SpDef / 4 Spe would have yielded more bulk and provides a Regen and hazards number?
Great team and congrats on the success!