Why is the reward from downing a boss simply the same as from killing any other trash?

The Red heads should give something more than the usual, or at least the % chance on something 'good' be improved significantly.

The Nemsis types should drop a Legendary every time they go down.

'The Boss' at the end of each Expedition map should also drop a Legendary and have a higher drop rate on the 'good' stuff.

As it stands unless you are OP then simply avoiding anything 'difficult' except the last boss is the way ahead.