Though it may be of limited consolation, many of us have made the same mistake- NWN2 always maintains an unwalkable "gutter" around the periphery of all exteriors- this allows the builder to "show" some of the surrounding area and make exteriors "feel" larger- I had to account for this in the early days of NWN2's release in coding the seamless AT scripts (as you could no longer base, say, southwest ATs, on proximity to 0,0 like in NWN1).
What you can do when "tiling" exteriors is tool the "gutters" to match the start of the next area- I believe GF's tutorial has some information on how to shortcut this, though I never got around to trying it myself.
Tanita's Terracoppa is the easiest way I've found of filling in the "gutter".. just a simple matter of cut and paste your source tiles to the destination area..
be careful though.. I seem to get the majority of my crashes about 2-3 hours after using it and then laying placeables..
but hell, if I fart the damn thing crashes and wipes my work
On indefinite real life hiatus
[22:52] <Veilan> obviously something sinister must be afoot if a DM does not have his social security number in his avatar name!