Wake vortices will generally descend at around 2 m/s or 300-500fpm depending on who you ask. They will persist much longer in still air conditions and, as is apparent from this report, conditions of little crosswind (the report states that winds were strong and north-westerly, i.e. directly behind the A380). All things being equal, offsetting by as little as a mile should be enough to avoid wake in more-or-less any conditions. But is this common enough practice?
I was thinking of a 380 overflying and another aircraft climbing from medium level to level 1000ft lower but only reaching that level 25 - 30 nm behind the 380. It may not be immediately obvious to the controller that there is a trailing wake problem to worry about.