You can probably look at the Hunter (ranger) mobs in Qvic, since they use bow and arrow when at range. Then just give the NPC 0 run speed so they are perma rooted. Then take off summoning so players aren't summoned within melee range, otherwise the NPC will always switch to melee I believe. Finally, if you want the whole fight to be done at range, you could setup a proximity on the NPC so that it will move any character that gets too close back outside of it's melee range.
Sounds like a fun encounter. Let us know if you get it working properly
