DEVS Please Fix GAC

No it doesn’t reward more. 

One question I have after that experience though, does it reward more crystals to be top at carbonite than bottom of whatever the next tier is?

Yes, and no. In the event itself, the rewards for winning/losing is the same. However as you progress through the ranks you'll receive crystals (premium currency) every day. The daily crystals will increase every time your rank does, even between Tiers within the same division.

Tried GAC 5v5 for the first time since getting my acct to level 85. about 490,000 GP and I was paired up with 3M GP+. I thought, maybe these are inactive accounts... But then I realized you have to actively sign in and then you have to actively attack me. 

THIS is exactly what I have been trying to adress - for a couple years now actually. Same reason why I really don't care too much what someone in Kyber has to say, considering they likely never even experienced matchups quite that bad.
As the game continues to grow (not necessarily much in population) the divide increases, as does the horrible match making for the event. The only way to really fix it is with an overhaul of some kind, OR with a reset - however if everyone gets reset in order to purge the nonsense going on most players will be incredibly upset. 

Frankly, I think a GAC should have a purge regularly and seasons should be 2 weeks minimum. The first week week would be a qualifier to determine where you fit best, followed by the next week which will determine whether your ranking goes up or down. If you're lazy and don't do much of anything, your ranking drops by 2 whole Tiers each round (if you have the higher GP) while if you win, with a lower GP each win gives you a 3-Tier climb within your division. This would mean if you are one of those high GP players endlessly sitting in Carbonite you'll remain there indefintely. If you have a new/smaller account you'll have a compensation price of climbing ranks very quickly, until you start being actively matched with opponents who are active, and on your level.
Or something like that anyway. I've been pushing out ideas left and right, and for the most part it feels like people would rather complain and whine about how inconvenient it'll be for them, than to try to come up with solutions themselves. Seriously the most toxic forum I have ever seen my entire life.