Did you install the bottom bracket yourself? (I've had the LBS do this because of the need to face the BB shell)
How many spacers are installed between the BB and the shell on the drive side?
The "standard" install says to put 5mm of spacers (A+B+C) on the drive side and 2.5mm on the other.
(See
http://cycle.shimano-eu.com/media/techdocs/content/cycle/SI/SI_1J10A_002/SI-1J10A-002-ENG_v1_m56577569830680226.pdf )
Might be worth playing around with this to reduce the chain line offset.
The Shimano spec says the chain line is 50mm, and this is fixed regardless, assuming the spacers are correct.
The road chainsets have a chainline of 45mm, and the 3-piece MTB cranksets can have 47.5 or 50mm depending on what spindle you put in.
47.5mm on MTB is equivalent to 45mm on road, because the hub is 5MM wider on the MTB, hence moving the cluster 2.5mm to the right.
You can offset this by moving 2.5mm of spacers from the right to the left of the BB.
The chain line on MTBs has been increased because of the prevalence of oversize seat tubes, which moves the front derailleur to the right, and makes it harder to set them up to shift well to the granny ring.
Also, the granny ring gets used a lot on MTBs, and needs to cover a much wider range of the cassette gears than on a road bike, so it makes sense to move the chainset to right to reduce cross-chaining.
Have you contacted Thorn themselves? The derailleur Nomad was a bit before the time of Hollowtech II cranksets.
A nice TA crankset with a tapered square BB might be just the thing...
