The trick to getting 1-10th place is to never play against NPCs. Winning against an NPC is roughly the same as tying with a PC. You want to aim for roughly 100 points a game. That's like tying half the games and winning the other half. Depending on the tournament, you don't even need to do that.

When you only play against PCs, you have a very good idea what cards they will use and it's not that hard to construct a deck that takes advantage of that. Most people from what I've seen just use the "auto" deck feature and that's incredibly predictable. Build a deck that takes the current tournoment's rules into account and you'll be better off then half the people you play against.

The most annoying part is waiting in the Battle Hall for PCs to pop up who are not playing against NPCs. That takes forever. If more people didn't play tournaments against NPCs, the rankings on the board wouldn't have as many gaps between the high-scoring players and the low-scoring players.