Work Visa Success Rates - Any Risks?

Hello all,

I did a quick search and I haven't found some insight to my question. If there is, kindly point me to it and apologies for repeating.

So, I have formally accepted an offer for a job in Bahrain (yay!) and have completed the following:

1. Medicals in early November
2. Police clearance about 2 weeks back
3. NDA

Now although I interviewed directly with the company, I'll be employed via a 3rd party, and I understand they'll run the visa processing. The company has asked a few times if I've submitted my resignation, and while I've told a few people informally here, I've not.

We've agreed my resumption date for early next year, but I await my visa - I understand it can take 30 days from application date. My questions:

1. Should I be concerned about a possible rejection of visa, even though I've completed practically all other employment documentation?
2. Based on #1 above, is it safe to formally resign current employment, can I assume the it's a mere formality for visa / work permit issuance

Just trying to manage the risk here. If there's a very low probability of a rejection, then it can be safer to resign. Are there any mitigations you can advise?