Yeah... Uhmmm... you are wrong about "purple" characters and at least the Vampiric Set too.
I've been thinking about removing a green talisman from my Harpy (Although my OCD wouldn't be too happy about that) because she NEVER goes under 70% health... She's at 24k, not 15k and she already hits like a truck, a lot of people here can confirm that.
They look so pretty (L)
The problem with the Vampiric set is not the proc rate, it's that they only work with physical damage.
Regarding proc rate, I feel they are ok. If you ever tried the Meteor or Comet set, they have a 70% proc rate IIRC, and that's not fun. As a person who finished the entire game, you don't need them to proc more. Not every talisman set needs to "fit or be good".
Finally, my Soldier Eddie, with almost the same amount of health as your Samurai Eddie, was never near being one shoted by that Imp. He hits hard for sure, in fact I'm pretty sure he deals true damage, but if that happens to you maybe your Eddie has something wrong.
Sorry, one more thing. I took the time to look at your characters, you have a Harpy, the Mummy Dog and the Demon as assassins. None of them are near maxed. The talismans are low level. I feel that you did not take the time to max them before saying they are, and I quote, "not worth using or upgrading".
Would you like to try a good assassin character with maxed talismans? Let me know.