After much work, managed to defeat a Legendary Assaultron hoping for some great loot after my labours of Hercules.

https://www.youtube.com/watch?v=8DVZCweK1X8

But no, just get an awful gun, 14 damage with 50% damage to bots. Of course, there is a small chance I will be only fighting bots for the rest of the game, with the remainder of enemies comprising humans, synths, mutants and more.

I am finding less and less reasons to play in Survival Mode difficulty.

Well they can also give overpowered loot, like just about any relentless weapon with over 50 base damage.

http://fallout4.wiki.fextralife.com/Relentless

With 4-Leaf Clover and Critical Banker it seems insane.

RNG is RNG.

This isn't Borderlands man...I don't think there was any guarantee of better stuff dropping.

Correct me if I'm wrong...

True, I have played Borderlands extensively, completely abusing the crate in BL 2. I initially thought of BL the first time I saw Legendary enemies, so why not add the same loot system?

Beats me.