The rank up bonus is exactly the best, not because I'm participating in duelbits signature but it is based on my own experience. A very simple example is that I received $200 rank up bonus for $250k wager in other casino but I received more than $350 if I remember it correctly in duelbits for the same wager.
Yeah they have set up their rakeback system in such a manner that it's for you to get to VIP levels like mentioned above for $1000 wagered you can reach first level.They are providing extra bonus to players according to their system and many have been benefited from this. Each progressive level rewards you with 12.5% of the house edge which is great boost for players.