It is a little troublesome to have such high DCs, as characters who have not properly maxed out their saves will pretty much have no chance of saving, or a character will have a very bad chance of saving on their bad save or something. However, I find that it really isn't all that hard to max out saves (I've a 15th level forsaker type who has a fort save of +26 with no magic, and a 20th level bard type with a will save of +38), the only problem is that some PCs don't spend a lot of time on it and end up being left in the dust. As long as you can find a balance between high DCs and high saves (saves are easier to max than DCs, I think) then it's not too big a deal to have a pretty high DC, I'd say. And Elminster's will save sucks, so it's not that big a deal to charm him ;-)