Workers on temporary working visas like you seem doubly exposed to exploitation: not only are they subjected to the regular shenanigans of employers, they face the threat of the employer pulling the visa.

Correct, and this was spot-on why I didn't raise a bigger stink about the bonuses. You get your visa sponsored through them... and if you want Permanent Resident status you have to work there for about 2 years. I was told not to expect any sort of raise or bonus during this time -- why bother since they know they own you? Painful.