1) if the mage can hit them with the fire thing, that could be a problem thats why creeps are surrounded by trees or above cliffs, I know water is great but, it could be more safe.
2) I would remove the house, if someone wants to wisp scout or peon scout, and wants to change route, I think the chance of agro is very low, 10%, but it may be, I would also complete behind with trees, to limit farm scouting or scouting in general and well maybe it can be more safe.