Heres how it is for me.
If you have NO tolerance at all to opiates, nor benzos. Their's absolutely a GREAT chance of OD, even in small doses.
If you have a HUGE tolerance to one of the substances, lets say opiates, but are new to benzos, the risk of OD greatly reduces DOWN, still possible with high enough doses.
If you have a HUGE tolerance to both benzos AND opiates, you're chance of OD is very small. BUT still possible if taken stupid amounts, like HUGE amounts your body is not used too.
Point is here, yes, overall, it IS dangerous to combine benzos and opiates.
Currently, I have a HUGE tolerance to opiates, nearly 9 years, from hydrocodone to oxycodone, and from heroin to methadone. Been on methadone (80mg last 2+ years), and it changed my life for the better.
No more lying, stealing, or any of that junky stuff you do your family they don't deserve.
Right now, my benzo tolerance is moderate, been on them for 6 months. I'm currently tapering off benzos as I post this to not get myself another addiction on my hands.
My chance of OD is very low due to tolerance, but like I said, still possible if taken stupid amounts.
I'm currently RX'd-
80mg methadone (daily, for 2 years)
5mg clonazepam (daily, just got it RX'd last week to taper off Xanax and valium.)