I don't see how darkcoin would be protected against time warp. It has retarget time 1 block and allows jump back in time for 6 blocks. Just generate 5 blocks stamped with long time intervals to get a low diff and then one block which gets you back to sync with official blcokchain. You get 40% of the official difficulty. Just repeat it until you get blocks almost for free so you can catch the official blockchain with your lousy miner. Then publish it and woohoo, your blockchain is now official blockchain.
All altcoins implementing 1 block retarget allowing blocks in the past are at risk.