All Dual-Classed NPCs (Imoen, Nalia & Anomen) have fewer weapon proficiencies when encountered than they should at their level. This is possible in player-created dual-classes due to secondary class proficiencies overwriting primary class proficiencies, but occurs in all the named NPCs.
When you first meet Anomen in the Copper Coronet at level 7 Fighter -> 8 Cleric he should have a total of 10 weapon proficiency points allocated. He has 6 points allocated, + in Warhammers, ++ in Maces, ++ in Slings & + in Sword & Shield style.
Imoen should have 6 weapon proficiency points. She has 4 allocated when first encountered, + in Daggers, + in Quarterstaff, + in Shortbows and + in Darts.
Nalia should have 6 weapon proficiency points. She has 4 allocated when first encountered, + in Shortswords, + in Daggers, + in Quarterstaff and + in Shortbows.
I appreciate that this may not necessarily be a bug but a design feature to prevent overpowered NPCs. None of these characters is particularly weak as a result, and this going unfixed would not be a huge drawback. Adding a couple of additional proficiency points to these characters would be much appreciated though.