Right now the ghosts are the best run a player can summon. So if you put in 100 tries then that player probably has a 1 in 100 shot of beating it. What this means is a person posting a 1000 ghost would have serious trouble beating 500 and have some difficulty beating a 250 ghost.
The win/lose logs that I have looked at reflect this idea pretty well.
Throwing in the stone blocks makes things worse because it helps the ghost.
How about reversing this for the player slightly by doing something different?
My suggestion would be to use the orb attacks differently. If you get matches of 5 it insulates you from the effect of the blocks (they cancel) or deletes them from the screen and if you wind up with additional orb attacks saved up at the end of the match, each one subtracts some multiplier (and or points) from the ghost.
The idea being that right now the ghost has the advantage, and it might be more fun if the player were given a slight edge to compensate for # of tries going into making the ghost.
Thought about it some more and have another idea to add to it.
Due to the asyncronous combat, it appears to be a asymetrical battle with the player getting just 1 shot to beat the ghost.
How about evening this up by letting a player get as many tries as they want to beat the ghost and making it only count as (1) battle. This would compensate for bad luck on the player, and the obvious good luck dozens to hundreds of tries the ghost gets. This would even things up and make it so two equal players could just barely beat or tie eachothers ghosts rather than have the puzzled (I can't believe my ghost beat you because I can't beat yours!) that I have seen so many players express.
I still think the orb attacks needs tweaking because it gives too much advantage to the ghost.