The big green lizards also always drop at least one Glyph of Envy and several exalted items. The set items are meant to be a bonus that matches the colour, rather than the main reward of that lizard type.
Set items are in a bad place in terms of balance and design. They’re largely underpowered and are dead end items with no way to upgrade them. We have plans to add a system in future that allows you to do more with them. But until that’s in, set item rewards are relatively unexciting, and we’re aware of that.