Rather than considering how powerful different items are in a one-to-one comparison, I think most of my distaste comes from how certain items stack and when they max out. For instance, there is no real general trend between rarity and stack-maxing; you don't benefit from more than 7 white Rusty Knives, but a green Will-o-the-Wisp is never undesirable. Furthermore, some items are (very smartly) designed to keep constant desirability by increasing the magnitude of the effect (Will-o-the-Wisp, Fire Shield, Headstompers, Gasoline, Ukelele, Mortar Tube) but other items will stack additive chance (AtG Missile, Rusty Knife, Lens-Maker's Glasses) which always leads to maxing out at 100%.
Though I'm not certain if there's a hard cap on Tough Times, I appreciate how the armor formula naturally gives diminishing returns, and think that additive chances should change to work the same way: for each Harvester's Scythe you have, you would increase from 1/100 to 6/105 to 11/110 to 16/115, and so on.
Code:
Scythes | Crit Rate Formula | Real Crit Chance
00 | 01 / 01 + 100 | 0.990%
01 | 06 / 06 + 100 | 5.660%
02 | 11 / 11 + 100 | 9.910%
03 | 16 / 16 + 100 | 13.79%
04 | 21 / 21 + 100 | 17.36%
05 | 26 / 26 + 100 | 20.63%
10 | 51 / 51 + 100 | 33.77%
20 | 101 / 101 + 100 | 50.25%
40 | 201 / 201 + 100 | 66.78%
100 | 501 / 501 + 100 | 83.36%
200 | 1001 / 1001 + 100 | 90.92%
2000 |10001 / 10001 + 100| 99.01%
But most importantly of all, I think a good item design in this game revolves around ensuring that any item can have at least one class that very much loves to have them, rather than necessarily balancing an item's general usefulness against every other item that exists.