I think the problem is that 0.17 reworked the mining calculation and it now works much more like oil where the base yield is determined by entity.amount / resource.normal. Ore patches tend to start with an amount in the hundreds or thousands (depending on richness), which then leads to yields of multiple ore per mining time. I'm not sure there's a way to fix this other than changing the amounts in the ore patches to exactly match resource.normal. When the module is first loaded it would have to modify all current ore patches. It would also have to update new chunks as they are generated.
Even so, that may not be ideal. If you use a normal of 100 then that means all of the ore patches appear "sparse". If you disable the mod after having used it on a map (and entity.amount having been changed everywhere), all of your existing ore patches will then have 100 ore left per tile and get used up very quickly.
Another option would maybe be to use a larger resource.normal and resource.minimum (say 1000 or 5000) and then set the entity.amount to that. That would fix the appearance of ore patches and would also revert to something a little closer to normal if you disabled the mod. You'd probably want to leave oil at 100.