Spirit mechanic not rewarding enough to bother with

Just got my first fox spirit, it turned a mob into map boss. I fought it with 3 other rares that had pulled with it. It was super fun and intense fight that lasted several minutes. I almost died about 4 times, and was super stoked when I killed them all..... only to drop a regal shard, not even a regal orb, and some worthless blue and rare items. This was all done on a T15, 6 mod map with 81 percent increased rarity I might add. Needless to say this was a big let down.

I find the same problem with challenging boss fights while leveling. You spend 5 to 10 mins in an epic battle with a boss who can one shot you with several mechanics, and when you finally succeed and kill them, they drop a blue item and maybe a pile of 50 gold.

Hard mechanics should always be rewarding, even if its just a few exalts or other currency. I understand the drops are not going to always be divines or super rare uniques, but a regal shard drop from a T15, with a legendary spirit, on a 6 mod map?