In base 5e, a staff of healing can be treated as:
1) A 10 charge Cure wound staff that gains 7.5 uses/day on average.
2) A 5 charge Lessor Restoration staff that gains 3.75 uses/day on average.
3) A 2 charge Mass Cure Wounds staff that gains 1.5 uses/day on average.
In your system, such items would have vastly different properties than the staff of healing would.
A 2 charge Mass Cure Wounds would probably roll 1d3 for its charge die, but it would never die from a single use.
In your system, it rolls 5d8 and has a great chance of fading from a single use.
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At some point, given how much more similar your items are to scrolls that you can sometimes use twice, you might not want to model your items after 5e items at all.
The connection to 5e items (the charge use = dice rolled) doesn't seem to yield any benefit. The balance points are way different, both between charged items and between charged items and non-charged items, that any rarity info 5e provides is dross. The use by characters is also extremely different.
This seems to be a system in need of a purpose.
If you want a ring of the ram in your system, just invent stats for it.