Without getting too deep into their actual statistics, I basically see mages as extra-expensive archers, so a lot of my planning has to go into where I'm going to have to throw away a bunch of resources and building sites because there may be ghosts coming through that way. This starts getting really cumbersome once there are a bunch of different routes in a level. I'm only about half way through so I don't know what happens with them later, but right now every level is a little more obnoxious when it comes to dealing with ghosts.
I love everything else about this game. The level design and all the different enemies are great. The giant mobs are a really cool extra thing that sets this game apart from other TDs. There's just one really wonky balance issue with this one enemy and its one weakness.
This would be one of my favorite games on Kongregate, if it didn't lean so heavily on a very frustrating random number generator. Having a 90% attack fail 6 or 7 times in a row a few times is enough to put me off even if the rest of the game is great.