Azriael,
Well, I'll support you in whatever you and Duckluck decide to do, but here is my opinion:
I really like Kadar. He fufills a lot of functions, and is an awesome character that is a synthesizing agent within the party (helpful with "grumpy" characters like Baba and "barmy" ones like Linji). In addition, several of your skills (such as Spot, Listen, Diplomacy, Sense Motive, Move Silently, and Hide) may also be covered by other members of the group -but this isn't a bad thing -it means that nearly all the party can be good stalkers,scouts, and such, without having one cluncky guy, waking up all the dead when the party travels.
So, I really hope that you stick with Kadar -I don't really see a big need from a metagame perspective, and from a role-playing perspective, I think he is perfect.
As for losing two players/PCs:
Perro never really seemed like he was going to make it (no offense Perro). Although his character concept was cool, we didn't modify our PCs to leave some gap for him to fill.
As for Cortek, well that's a different matter. While Kadar, Linji, and Mrek (if he can flank and sneak attack) are all pretty decent at hitting and not getting hit (compared to average PC statistics), Cortek was our meat shield -and now we lack that. This gap is made all the more severe since we lack a true cleric/healer (M'rek does have a wand -as does Kadar, and I will go ahead and work toward having Linji become a Sacred Fist, so we are compensating to some degree).
Duckluck & others: Perhaps we can open up the campaign to one other player -I know of a few who would love to do so on Planewalker (can't say I know any of them close enough to personally vouch for them though). So as not to slow the campaign down seriously, perhaps set some deadline for character proposals (maybe the end of the week?).
Just tossing out ideas -and we could also add some stipulation that the party needs a meatshield/tank, and/or healer.
What does everyone think (especially our DM)?
EDIT: it seems that Duckluck posted while I was finishing my post, and his comments essentially void most of what I had to say -so, uh, nevermind.
I don't think that's necessary. If you look at it, you have a slightly-squishy melee combatant, a very squishy (but also powerful) secondary melee combatant, a stealthy guy who makes a good flanker, and a rather powerful wizard (that Illithid Vampire was lucky he had Fast Healing). I'll just scale back the difficulty of the upcoming encounters, and remove some of the emphasis on front-line melee combat. Of course, this is all assuming Korchuk won't return, which I'm not convinced of as yet.