After thinking about it for a long time, I've finally come to a conclusion: It's not Weapons or Classes that make LD unbalanced. Indeed, many of them would probably be balanced according to this, with the exception of a few specific weapons, like Cutters, Shard Bombs, and Winmillion.
However, there is one thing which just makes it very...unbalanced. That is: Heart Trinkets. No drawbacks are on them. At all. I can put on two, in fact, and I only get benefits. There are few things I would want to trade them for, and those things could be 'easily' obtained through UVs. (Looking at you, modules.)
So, changes I think should be made:
Compassionate Penta Heart Trinket: 6HP, Attack Damage Decrease: Medium (red)
Iron Penta Heart Trinket: 6HP, Movement Speed Decrease: Medium (silver)
Merciful Penta Heart Trinket: 6HP, Charge Time Decrease: Medium, Attack Speed Decrease: Medium (blue)
1-4* trinkets, should be the same as they are now but with damage decrease: low.
Current Penta Heart Trinkets would become Compassionate Penta Heart Trinkets.
Wouldn't this further promote damage-based armor rather than make defensive armors more useful, thus decreasing balance to the game overall..