The >51% situation is the same for many alts (think of "rare" MM coins like DVC or IXC and BitParking, they also have >90%).

Of course it's suboptimal, but it doesn't make the coin worthless. It merely means that miners have decided to trust a single entity to pool their efforts. Nothing more, and, granted, nothing less: trusting a central entity is not the aim of crypto coins IMO, at least not the original Bitcoin.

Miners could, theoretically, at any time, move away from CoinMine.pl and solo mine and/or switch pools, if they no longer trust them, or if they are no longer pleased by their policy.