So significant/huge >12%?

The developer premine coins aren't in public possession (unless they dumped them? but I'm not sure if the rules even allow that yet).

That is overstating things. Reading through the thread, it is abundantly clear that the devs and other early adopters believe in the coin and are not planning a massive dump. 

IMO this is a feature -- not a problem or a scam.  Basically, it allows for the devs to have a more fine control over how the coin is released into the market; and thus prevents a “mid-life” dump via multipools and whale miners that troubles many a coin once the price starts to rise.  As mentioned above, if a coin is super-popular from the beginning like Doge then there is no problem as it gets distributed to a wide range of miners.  Even if whales or whatnot show up later there is a big enough dedicated mining community that in effect prevents these entities from negatively effecting the market. 

On the other hand, coins that don't blow up from the beginning and slowly rise in price due to the efforts of the early adopters, inevitably get attacked by these whales/mutlipools -- and the diff increase alone never seems to be enough to prevent a ton of coins of entering the hands of the few.  When these coins get dumped... the market crashes.  The way Darkcoin is currently set up this cannot happen.  And yes, even though Darkcoin is multipool resistant – it is still vulnerable to whales (it was actually getting hammered before the diff /reward system was enhanced by KGW).

Now, I know it may seem unfair to latecomer miners and some trolls even went as far as trying to discourage people by calling this a instamine. But the thing is... the vast majority of coins have a high percentage owned by early adopters.  That is the reward they get for believing in the coin before anybody else.  Due to the diff/reward system Darkcoin might be a little more extreme, but as I just explained that system has a very important purpose.

Lastly, it is not like the devs are not willing to respond.  Take a look at the diff/reward chart below. 

The blue line is actually a hardfork that was put in place a couple of weeks ago to be ready for GPU miners (GPU client first released last week) so that reward wouldn't drop to zero once the hash power went through the roof. 

Tldr; This is a fair coin. The diff/reward is a feature that allows more fine control over how much coin is released into the market and thus prevents manipulation by whales who plan to dump.