I've only been playing RPG's since I got to college five years ago, so I've had little exposure to many systems. Of the systems I've played in, I only remember the rules about armor for Earthdawn and D&D.
And armor providing damage reduction isn't the only thing that's shared....the different forms of alternate forms of vision, Dwarves had heat-sight, and Elves had low-light vision in ED long before 3rd edition. Also the idea of multiclassing by adding a class later on in your career, as opposed to the 1st/2nd edition idea of choosing your class(es) at 1st level (besides humans and dual-classing).
And as I said before, d20 lifting ideas from Earthdawn is a good thing. Isn't that the point of the d20 system, take the good stuff other people have done and add it to your own system.
Wolfspider, you mention lackluster sales for ED 2nd edition. Where have you seen these numbers? It hasn't been terribly long since it was released, what, 3 months? Just this last Thursday at my local WotC store I saw that two copies of ED2 that were there last week were gone this week. I was quite pleased and surprised to see both copies go in one week. Now I just need to meet these two people and finally get a game going.
Don't get me wrong, I love D&D, it's a real close battle between D&D and ED as to which I like better. Which is saying a lot considering my groups view of D&D towards the end of 2nd edition.
As for the "problem" with the core classes of Shadow Chasers, I remember in the first story about Shadow Chasers that it was said that it was part of the plan to have people take a prestige class. The core classes were simply a means of giving some manner of definition to the character before it achieved a PrC. But this similar vitality die, and armor only helping with wound damage really sounds like poor design work. I, too, hope Star Wars doesn't use it so poorly.