Sorry, but you seriously do not make sense.
First off, you assume that it is easy to get the best poison in the game (regardless of finding it adventuring, buying it in a shop, or camping out and killing Purple Worms). That doesn't happen at all tables.
Second, you assume that Purple Worms are easy to find. Again, not at all tables.
Finally, you assume that Purple Worms are easy to kill. Not in my game. A Purple Worm is a predator in my game. It might be dumb, but it doesn't just attack PCs above the surface of the earth. It comes up from under the ground, bites its prey, swallows it, and then burrows back underground. Often all in the same round. The other PCs can often follow, but that doesn't mean that it's easy. The Worm might burrow straight down. It might burrow through dirt where it's easy to for it to collapse. I've had more than one PC in campaigns buried by collapsing Purple Worm tunnels, especially in dirt.
And one of the situations that can occur with Purple Worms (at least IME) that does not typically occur with most monster encounters is that if they are burrowing through rock or ground and regurgitate one or more PCs, those PCs now find themselves in pitch dark, with the mouth of a Purple Worm a foot away, and even if they do kill it, they could still suffocate or get crushed by its dead body. Some DMs play the game to make sense. Gargantuan bodies of creatures do not just magically disappear.
I find it a bit funny how you assume that an item in the DMG (or monster in the MM) is easily available to find, and that if you create an absurd damage chart that uses that item, that all damage charts must be suspect. This is not the case. Some situations are common and some are extremely rare. Your example was beyond extremely rare. It would almost never happen at most tables. Bless? It happens at nearly every table. The other charts in this thread are reasonable, yours was not.
Sorry, but your point is invalid.