No, that is the save mechanic. But, there are various bonuses. My eladrin ranger got a +5 racial modifier vs. Charm, for instance. I don't know if there are powers later on that up the DC as it were, but I would assume so.
Agreed. I'm assuming there will be special powers/feats/etc that make it more difficult to succeed on a "4E Saving Throw", just as it seems that there are powers that make it easier to succeed on such a Saving Throw.
So a 20th level ArchMage probably has special powers that would alter that Goblin's saving throw from "Roll a 10+ to end effect" to a more appropriate "Roll a 20 to end the effect".
If that's not the case, and it turns out that Saving Throws are always a flat 55% chance to succeed, regardless of any other factors, I'll have a good laugh at the sheer stupidity of the concept and then houserule it away.