Scayde, it sounds to me like you'd enjoy playing an Evil group. Of course, there's a lot of disagreement about what constitutes "evil", so it's up to you to decide on your own definition. Usually, in the evil point of view, strength, not character, determines personal worth, and people should be rewarded for what they earn, not for what they "deserve". Take a cue from the NPCs. For example, Korgan enjoys killing and looting, and he believes in the survival of the fittest. He has some good lines in Throne of Bhaal: "Killing is our business, and business is good." When he throws himself into battle, he cries with glee, "Now we're getting down to business!" Some people would argue that he's not truly "evil" because he's not a mindless killing machine that kills everything in sight, but I don't really think that's how the evil value system works. Korgan has a soft spot for children, and he doesn't mock the gods. But give him a bounty or tell him that someone else will get the gold if he doesn't get it first, and he'll pull out his axe and go to work before you know it.
Minsc, on the other hand, believes in justice and righteousness. He will kill people if they deserve it, but his primary motivation is to be a hero and all that being a hero entails. Some might say he's a glory hound, but I say he's just exuberant.
I don't think he fits into your party, whether you can use his skills or not.
Viconia and Edwin would fit right in with your character and Korgan. A party like that would give you all the evil NPCs there are in the game (until you get to Throne of Bhaal). You could argue that those three characters are the strongest NPCs in the game. I suspect that it was done on purpose. No character is perfect, so Viconia has her weak points (low strength and low constitution), but there are items and spells that can easily make those shortcomings irrelevant.
The problem with replacing weaker NPCs with stronger NPCs as you go along is that the ones you end up with in your party will have missed out on a lot of experience by the time you decide you want them. The game tries to make adjustments by changing the level of the NPCs you meet based on your own level, but I'd rather get them as soon as possible and level them up myself. Besides, if they're the ones you want in your party, why would you do a bunch of quests without them?
To meet your need for a thief, you could make your main character a Fighter/Thief (one of my favorite classes) or recruit Jan or Imoen. Neither of them is evil, but Jan is entertaining (if you enjoy his kind of humor), and Imoen, who is pretty quiet for the most part, will stick with you even if you're rotten to the core.
Having Jan or Imoen in your party will also give you a second Mage, which can come in handy. (I don't recommend making your main character a Mage/Thief to fulfill your need for both a Thief and a Mage, but I guess that's an option. But I'd rather have someone who can deal out damage in melee.) Then there's the Fighter in Throne of Bhaal who's even better than Korgan. A small party (four or less) has its advantages, but a large party (five or more) can be more interesting because of the NPC dialogue, if you are interested in that sort of thing.
When I asked you, "What are you trying to accomplish?" I meant, what has been important to you so far? Have you been trying to rescue Imoen as soon as you can, or have you been trying to form the most powerful party you can, or have you been focussing on killing Irenicus, etc.? Do you feel like people (like the Shadow Thieves) have been jerking you around, and would you like to kill them for it? I also wonder what you did to make your Reputation drop to 6. Did you kill an innocent person in the streets? Did you get caught stealing several times? You don't have to use ShadowKeeper to raise your Reputation. As long as you can enter a Temple without being attacked and have some gold, you can raise your Reputation by donating. Obviously, everyone can be bought in the city of coin.
There's a difference between finding as many powerful items as you can and
being powerful. Power is enormously affected by your skill as a player, not simply by the way your characters are equipped or how many hit points they have and so forth. I think that learning how to buff up your characters, learning battle tactics, and using spells with finesse are the real keys to success, not just hitting your opponents with powerful weapons. I think it's great that you're willing to learn what you can and try new things to see what works best for you. IMO, that's the best way to play.
