Well, I was assuming you were more looking for a “Am I unlucky with RNG?” answer and not really what followed. 
No, you misunderstood me. Higher scaling will always give you higher chances for getting more exalted gear.
Basically, corruption will affect the chance that any given affix will get pushed to T6+.
LE works mostly with reroll chances. This means that you will roll for something, then try to hit the reroll. If you fail the reroll, it will roll something else.
This works for many things, like which unique drops:
-Higher uniques have a high reroll chance. Red ring, for example, has a reroll chance of 98%. This means that when the game rolls for a unique ring, if it lands on a red ring, it will roll again. If it hits within the 98%, it wil reroll a different ring.
-Common uniques don’t have reroll chances, so when it lands on one, that’s the one that drops.
This also works for rarity:
-The game will roll for item rarity. If it lands on unique, it will reroll. If it fails the reroll, it will drop down to a regular item.
This also works for affix tiers:
-The game will roll for tier. If it lands on exalted, it will reroll. If it fails, the item is rare.
I assume the same thing applies to the rest of the tiers. I don’t have confirmation of this, but it seems to fall in line with what they do everywhere else:
-You roll for the tier in one affix. If it lands exalted, it will reroll. If it fails, it will be T5 or less and the same for the rest of them.
-Then you roll for the next if you haven’t failed the previous one. If it lands exalted again, you reroll once more. If it fails, the rest of the affixes are T5 or less.
-etc.
That means that the chances of hitting the reroll with success multiple times drops drastically the more affixes you have. Which is why 4 T6+ affixes are so rare.
And, getting back to the original point, corruption will simply make it so that the reroll chance ends up being lower, so you have more chances to hit it. So the more corruption, the better your chances (they’re still small though). This will also apply to rare uniques.
As a sidenote, I will also point out that corruption has been heavily modified with 1.0. So information from previous versions might not apply.
In any case, you can see the item rarity modifier when you’re doing echoes. The higher it is, the easier it gets to have better items.
That will really depend on what type of player you are. If you focus on a few characters only, then yes, MG is much better.
But if you like constantly making new characters, and they’re all CoF, then CoF Is better.
The reason for this is that MG has a larger pool. But the odds of a good item are smaller for any given player than for CoF players. Which means that the really good items are very rare, expensive and usually sniped by the top 1% players.
Whereas CoF has a very good chance to get “A” BiS item more easily. It might not be “The” BiS item you need for your build, but it will be one for a different build.
So if you don’t play many characters, or if you don’t really care about min-max or pushing a build’s limit, then MG is great.
But if you like to constantly make new builds, CoF is great. I have 30 or 40 stash tabs with exalted gear. When I make a new character, I almost always have exalted gear ready for them. Many times even excellent gear.
This is made even better with the new runes that let us manipulate the exalted affixes.
The problem is that those items will be extremely rare in MG and very high price.
The search UI also doesn’t help much. You can’t really filter for “triple exalted”. You have to search specific affixes instead.
I should also point out, because you’ve said something about it before, for slamming uniques you don’t need the exact base. All you need is the item type. That means that if you want to slam, for example, a Phantom Grip, you don’t need to find the exalted affixes on a copper ring. Any ring will do.
This also applies to the rune of ascendance.
In Patch 0.9.1, the devs explicitly confirmed that higher corruption increases the chance for T7 affixes.
Source: Patch notes & confirmed in dev posts