On what sort of character? You can get +4 Insight on a ring, cloak, Alchemical crafted weapon or shield, or Epic Swashbuckler. You can only get +4 Dodge on the Icy Raiments or Epic Staff of Nat Gann. Adding both
would be too strong, as the Belt + Gem would give you +8 AC, +5 Protection (or +6), +4 Insight and +4 Dodge. That feels like a bit too much. If you're a monk-based AC character, this would let you swap the Icy's for something more useful, like the Frozen Tunic, Red Dragonscale, Garments of Equilibrium, DT, or something else and keep your +4 Dodge. Meanwhile, it opens up the possibility for paladins and fighters to get +4 Dodge, though it competes with the defender ToD sets (+2 AC among other things in the belt slot for paladins, neck slot for fighters), and Epic Grim's Bracelet (+3 Dodge in neck slot). There are ways to work in this itemization, but it poses some tough choices. Having both +4 Dodge and Insight would probably make this a must-have set, which will limit overall choices.