AMNIS2: apparently intended for the Nashkel barracks, but for some reason he got replaced with HICK. Not sure why, since AMNIS2 has more to say than his counterpart.
ARCHDR: seems to have been replaced by DRUID2 for reasons of game balance (ARCHDR even uses DRUID2.dlg). He's level 12 and calls Seniyad his superior in his charmed dialogue, so Seniyad was probably originally supposed to be something like level 14 rather than level 9.
ARKANIS, CANDER, DEDER, MORDAI and OSPREY: the temporary party members in the chapter 1 training sequence.
AVERY: Six could also be thinking of Black Isle's Doug Avery, producer on BG1, SoA and ToB
. Whatever the case, his dialogue file is blank, so it seems likely he's not in the game.
BART8: supposedly the bartender at the Elfsong (AR0705), but BART11 appears there instead.
BART9: supposedly the bartender at the Helm & Cloak (AR0116), but BART12 appears there instead.
CASSON: Tremain Belde'ar's son, whose body you retrieve from the temple of Umberleee.
CORSONE: appears after you kill Osmadi in Larswood and claims to be a companion of Osmadi, but turns out to be a shadow druid who poisoned Osmadi and his group.
DEAGAN: according to his dialogue, he approaches the party and asks them to go see Aldeth Sashenstar in the Three Old Kegs. However, since Aldeth is hanging around outside the Merchant's League building (only if you sided with him back in the Cloakwood, of course) and not in the Three Old Kegs, I'd think it's a safe bet that Deagan was cut.
DROTH: the ogre mage who "owns" Shoal the Nereid.
DRUID2, DRUIDC: most likely were going to appear alongside Seniyad in the Cloakwood, but Bioware decided simply to use three copies of DRUID3 instead. Incidentally, for some reason DRUID2, DRUID3 and DRUIDC are all Neutral Good Clerics
.