27% of current poe ninja Mamba Viper Strike users use Sadism.
None use multistrike.
Assuming you match your poison duration to expire before the last attack, wouldn't it be a good idea to run both to make use of the 2nd or 3rd(awakened multistrike) repeat more multiplier?
It'd require some duration and APS breakpoint crunching but seems sound in theory. Think this would be worth trying?

Thoughts?> https://pobb.in/Egkh6-Ylp3Km

Also, If you test with:

Adds 187 to 294 physical damage
Adds 98 to 140 physical damage
Adds 98 to 140 fire damage
Adds 98 to 140 cold damage
Adds 1 to 250 lightning damage
Adds 98 to 140 chaos damage

Ie 67% more poison dps, not 100%.