I LOVE sub LO Garchomp. Thing is fantastic.
Try Venusaur over Lilligant on that Sun team. It doesn't get poisoned, which is good vs Rain stall. It also uses Sunny Day and is bulkier, which is good vs rain stall. The team already has hydreigon and starmie.
You need to understand another thing. To make it to round 5 or 6 in a large tournament, is lucky. Regardless of the circumstances. It takes luck to not be hurt by team matchup, or not to be hax'd out.
When I did well in tournaments before, I considered myself lucky for not getting hax'd, or not fighting really strong opponents who can beat me, or not getting a bad team matchup. Or heck, even getting help with a wind of hax here and there.
I would consider a lot of people in ST9 lucky lol. Don't consider yourself a downer because you lucked 2-3 people in this tournament. I was there before.
Losing might be a wake-up call to you. It might make you stronger as a result. Knowing what you did wrong, and knowing what you were up against - in the premier smogon tournament.
Now go enter non official tournaments and have fun. They are generally easier, more fun, and less stressful than the one you just entered. Although you didn't actually fight a famous player yet.