A second dps poison we'd be 100% balanced around. No thanks, we've been down that route.
Can you imagine being asked to run crippling poison over instant or deadly? It would blow up your damage. That's the opposite of utility.
I think that if any of these mattered:
The leeching poison heal
The leeching poison shiv
The mind numbing poison effect
The mind numbing poison shiv
Then we'd see some actual utility. Meanwhile, there's a few fights where cripple (or shiv cripple) matter, but generally other classes bring it with less drama. The paralytic stun works on Horridon adds, the paralytic root works nowhere (and you are probably better off with prey).
These utility tricks just don't work that often, that much. I think you could safely boost leeching poison's percent heal as a start.