This is a bit different for the PoW/PoS hybrid. While a well connected node with a plenty of the hashing power may win the race in broadcasting its PoW block it can't make the network accept more PoW blocks than the network would accept according to the 12/1 rule. ATM there should be no big coinstake in the malicious hands to influence PoS either.
As I posted today at some moment we even were behind the target - we had 22 PoW blocks out of 326 while expected number is 27.
What makes you say that? What ever happened to the 500,000,000 pre-mined coins?
If you follow the blockchain, the genesis block starts off with 500 million.
500000000
98sNiCGjGK6L4ukoxTQvW99Mxx3SxFLqUW
This is split across 2 addresses (99 million and 401 million):
99000000
9Bw85xV9FjcZ3X9iFKoVXpAwNmM6JNfZ1R (Still retains a balance of ~99 million)
400999999.98
9A5mtFtxzmN7fhWmkPFWmES8bXW6Bu4Kc6
If we follow the remaining 400 million to that second address we see another split (99 mil / 301 mil)
99000000
96ypKUJmNaZEQGkbzkemBfb13GCxYvFhkx (Still retains a balance of ~99 million)
301999999.96
963vUdcoxt6ydVoycreBWh4StgYTbmaF4L
Follow the remaining 301 million to the next address and it's split up again in the same 99 million amount:
99000000
9DX56airvFLUB1RL9DDwLgV4nzhZdY7FMB
202999999.94
9Lnt3uR84usNHs8eDs7uk1wjpKYtTTHsNX
Following the 202 million remaining, you can see many smaller 5,000-20,000 GRA transfers (presumably the giveaways).
So, at least a few wallets were sent ~100,000,000 GRA and the dev probably still has 150-200,000,000 more.... That's actually quite a large amount of GRA (and a significant part of what has been mined) concentrated in just a few wallets.