If you are using vanilla NWN (without Tony K AI) then Tomi will act as a suicide bomber unless you keep on giving him orders like "holding position" and then "attack nearest" when it suits better unless you are the first going on attack (this way you could take benefit from his sneak attacks).
Assuming you installed Tony K AI you need to equip Tomi with two weapons (the offhand one being one level below the first one, i.e. Shortsword +2 in the right hand and Kukri +1 in the offhand) or he will more likely reverse those weapons using for example the smallest weapon in the right hand if the magic modifier is higher.
With the new AI you can even ask Tomi to get stealthy all the time.
Personally I find his ability with the shortbow more effective, the tactic that I suggest by far is to make him use his ranged weapons until the enemy gets within 3m (yes, you can ask him to do this thru Tony K AI) then he will switch to melee weapons.
SPOILER:
by levelling up Tomi will get improved crit on his kukri and will focus on his shortbow, not only, he will achieve rapid shot which is like having artillery behind you in aid (sneak attacks included if he's not too far).
