Conversion to Cold Damage Mechanic Confusion

I've read the damage conversion mechanics and it makes sense to me, except for one thing.

Conversion on skill gems takes priority over everything...okay I can accept that.
Conversion on gear takes priority over the passive tree...what?!

The passive tree IS the character, it doesn't make any sense whatsoever to me that gear should out-prioritize the passive tree.

I was kind of hoping to turn Xoph's Nurture into a cold bow*. I knew the 60% phys to cold conversion on Ice Shot would take priority over the 50% phys to fire on the bow (and reduce it to 40%). I expected the 2 20% phys to cold nodes (Weapon Cold Damage, Winter Spirit) I had to cover the rest. Guess not.

*I was hoping to pair Hrimburn with it to get cold ignites & prolif + chill/freeze, just for something to play with.

Someone that has more experience my have different information, but here is what i found when i was researching this for a frost blades character. In the event where you have more than 100% elemental damage conversion, the different types (fire, ice, etc) are applied at a prorated percent based off of their total of the whole. The way I understand it in the situation you described, you would end up with 66.6666% cold damage (100/150*100) and
33.3333% fire damage (50/150*100).

There may be vets that came up with different information and I hope they weigh in if this is not the case.

Oh I get that. Skills take priority, and all other conversion on gear gets scaled. So Ice Shot @ 60% cold conversion would reduce Xoph's in-built 50% conversion to fire, to 40%. I just wasn't expecting conversion on the passive tree to get lumped in with gear-based conversion. I thought it would take priority, just like skill-based conversion and edge out the fire conversion all together. It makes more sense to me that conversion on the passive tree should count first (and be un-scaled), then skill gems (still un-scaled), then gear (with scaling).