Is it intentional that the last blue monster to die carries most of the loot?

After killing many, many packs of "blue" monsters, I've noticed that the last monster in a group usually seems to drop far more loot than his other blue brethren. I can't say that it's always, but it certainly feels like it happens more frequently than just random luck.

Is this by design, or am I just happening to roll better loot more often on the last monster?

This is certainly intentional.

The last monster in a group of champions drops the most loot because that is your reward for defeating the entire group. You will always get a better roll when defeating the last one.