You are a:
I am pretty prehistoric, but not extinct,
Horseshoe crabs are one of the oldest species still extant
it would be hard to miss me if I blinked.
From Wikipedia: 'the animals have the largest rods and cones of any known animal, about 100 times the size of humans'
I do not drip ruby life juice,
Horseshoe crab blood is blue
and my tail is even pointer than that of a mongoose.
Horseshoe crabs have a notoriously pointy tail
You might think I am the lucky one, but it is you who benefits when all is said and done.
Horseshoe crab blood is farmed for use in numerous medical therapies.