That came back in Diablo II too eventually in the form of rune words, and I don't think it really worked out too well in the end. I do think it actually could be designed and implemented properly; balanced, etc. but...
For me the more important question though is what impact does it have on the class you're playing and also our knowledge of the Diablo world? Is a class nothing more than someone who read from a book, or is holding a specific item? No, they're very specific and very iconic figures (heroes even) from very distinct styles and backgrounds. The characters we play are these concentrated images of their cultures, beliefs, etc. Everything they do resembles who they are and where they're from, and what does it mean to then piecemeal that out to any one who just happens to throw a couple runes in to an item.
It worked better in Diablo (1) I think. Conceptually it was a bit easier to digest just because of the basic pen and paper underpinnings, and the heroes were far more generic. It was also far less obtrusive.
In Diablo II though, for me anyway, it always undermined the uniqueness of playing a specific class, and also what it meant to be that character. Aside from everything else it caused.