As long as the math is right, I don't see much reason to get worked up over this. Easy to adjust who does how much rolling without throwing off the game at your own table.
I do like static defenses, especially because of the rock-paper-scissors aspect of 4e. If anything I felt they didn't go far enough in that direction; it would be nice to have to adapt one's tactics more rather than less to a given monster. I dislike the "everything is effective against everyone" approach.
Despite my preference for static defenses, two things went wrong with 4e's base system. One is that duration is unrelated to the underlying defense. So, e.g., once a strong-willed character is hit with a charm spell they don't get free any faster than a weak-willed character.
The second is that save ends effects were generally awful. You had to hit them first, and then they lasted on average 1.5 rounds. Yipee.
So what I'd like to see is:
1) Caster rolls for instant durations.
2) Target rolls for everything with a duration on their turn. So at least give one round of effect before they break free for daily powers. (You can have it get worse after they fail a save, like 4e Sleep, but round 1 should be an Effect.)
3) Saves apply ability bonuses and are against appropriate modifiers, so that high-Con characters shrug poison effects more quickly, etc.
Any of those could be opposed rolls, e.g., a continuing battle of wills between a caster and someone he's mentally dominated. As I said, that's easy to change at any given table if the math is right.