Major edit suggestions for the future.
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The most important suggestion I can make for koth_sanctuary is to make three distinct rollout paths in which the spawn can be isolated, and keep similar rollout times for each path. This will remove many of the current issues that I am about to address.
The second most important suggestion I can make for koth_sanctuary is to isolate mid differently. The entrances and rollouts currently in place leave no room for Scouts to be effective at mids, and very overpowering Sniper sightlines.
The third most important suggestion I can make for koth_sanctuary is to have open paths into the mid from the three rollout paths.
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Minor edit suggestions for the future.
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-Remove the pillars outside of the spawn.
-Increase the size of the spawn room so that it's easier to heal targets at the start.
-Remove the V-bridge (will talk about this later regarding Sniper sightlines). This shouldn't be a problem to remove w/ different rollout paths, although.
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Other thoughts.
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koth_pro_viaduct comes to mind as an example of a map which isolates the spawn from mid with different rollout paths, optimal/similar rollout times from each path, and associates a high-risk factor with spawn camping.
Add a height advantage which can be played at mid to keep the uniqueness of the map, but make sure it can be countered and both teams have an advantage to play. Try not to box-in mid.
Lower the skybox.
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The map as is.
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I downloaded the map and looked over Sniper sightlines primarily, and noticed a ton of overpowering Sniper sightlines which need to be changed/removed, as well as some other details. Again, the first major suggestion I made will eliminate most of these issues. My thoughts and observations are on the Imgur links provided.
Sniper sightlines.
From point to spawn: http://imgur.com/7PzUE89 <- Probably the most important screenshot I took.
From spawn on rollout: http://imgur.com/crvgzZk
From V-bridge: http://imgur.com/5dXB17B and http://imgur.com/GlQ5any
-As the map is, add a bridge to prevent the first screenshot from being used: http://imgur.com/uzlnJFR
Mid.
Entrances: http://imgur.com/uzlnJFR
Wall pillars: http://imgur.com/tzUei47
Cheeky surf: http://imgur.com/uKZLAtR <- Not viable, but not a good feature none the less.
Accessible spots that need to be removed.
Spawn: http://imgur.com/aFmHncg
V-bridge: http://imgur.com/GeOdcis
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I hope this helps the development of your map, but there are a lot of major changes which need to be made before this is presentable/has a chance of seeing use.