There are not enough people playing Wakfu at all character levels for this to work. You are segregating the playerbase by level, which is never a good idea. Cooperation and interaction between players of all levels should be encouraged, not crushed.
Some of the most fun I have had playing this game is when I was underlevel for a dungeon but still carried my weight. It is satisfying making it through a tough fight alongside more powerful allies and getting rewarded for such.