In the interest of generating productive discussion on what would make Dominion more balanced, let's talk about WHY the aura does what it does.
Passive Exp and Gold
The goal here is to reduce the opportunity cost of constantly fighting/ganking. Yes, killing creeps makes you stronger, but sitting in lane doing nothing but that is the optimal choice far less often.
It has the side effect of reducing the snowball, which I consider a big plus. I don't find it fun to be in a game where a single mistake (especially one that can be made by someone else beyond my power to help) deciding the outcome early in a long match to be at all entertaining. Once a game is decided, I'd like to play then next one, thank you very much.
12% Armor Pen and 5% Magic Pen
These serve to make it easier to kill tanky champions, especially during turret dives. Armor pen is greater than magic pen because Armor values are higher. It makes fights shorter, without making it trivial to blow up a tanky champion unless you've a big lead, they're not itemized for you, or your blowing cd's on many of your own champions.
At those goals, I think the aura is mostly successful.
The side effect is champions do more damage while itemize defense, which makes bruisers stronger at diving squishies, making playing glass cannon types less effective, especially against bruiser heavy teams.
20% Healing Reduction
The point of this is to limit sustain. Especially with the mana aura, heal heavy comps could sit on points forever without the healing reduction. This makes it impossible to completely counter poke via sustain, and allows sieging down points to remain a viable option.
It has the side effect of hurting "infinte lifesteal" carries that can out heal tanks' damage. I believe classifying this as a good or a bad thing is a matter of opinion, with both positions having valid points. But since I play tanks, I appreciate it.
Increased mana regen with decreasing mana remaining.
In case you didn't know, the Crystal Scar mana regen effect is basically a free chalice of harmony passive where your mana regen increases in proportion to the percent of mana you're missing. (I think it's actually better than the CoH passive).
Since the intent of the game mode is to encourage constant fighting/ganking, this allows champions who can only go through their rotations a few times without exhausting their mana pools to be relevant without itemizing solely to counter this limitation. Base mana costs and regen are balanced (especially early game before you have a chance to really itemize) around the idea that you have to wait in lane until times when it's useful to use your skills, rather than more spamy play.
In other words, it's expect that champions will have at least some time to recover mana. This is not the case on the Scar, and something has to be done about it, or only champions with no/low mana costs would be viable.
The problem is this really beefs up champions like Yorric with really strong lanning abilities originally balanced by the fact that extended spaming is unsustainable due to mana costs, and gives manaless champions (including energy-based ones) much less relative power.
The crystal scar aura encourages and enables prolonged continuously fighting while making it more difficult to simply sit on a point forever without dying or recalling. While it generally succeeds at this goal, there are some definately unintended and often undesirable consequences.