Hi,

Going to start IWD enhanced edition and have some thoughts I'd share on character creation:

Paladin (Fighting skills, some spells and unique abilities) plus get holy avenger
Figher 1/2 Orc Chaotic Evil (STR 19 DEX 18 CON 19). Name is Bane. Allows me to use evil weapons. Hold off on points
in missle weapons and focus on melee. One point in blunt and others in weapons of your preference
Human Fighter one level then switch to thief rest of the game. Pts into CB, morningstar, swords (your choice)
Human Fighter one level then switch to wild mage. Pour weapons points on slings and one point on dagger
Human Ranger one level then switch Cleric. Gives you duel wield and can points into sling, mace, morningstar, hammer. Choose skeletal undead. Best choice available in opinion
Elf Ranger put most points in bow, one each in morningstar and sword

Bowman ability to attack at a distance and speed makes him almost a second mage as he can disrupt spellcasters as others have mentioned
And by taking just one level of fighter and ranger get to max out on weapon skills and switch over to your main class (Thief and mage) before leaving Easthaven
I also have no issue with adjusting stats in character creation so if you want to, go ahead and do it. How else do you think my 1/2 orc got those superman stats?

With the 3 dualclasses the game will be easier but if you have some skill pure classes will probably yield the better gaming experience since the characters will be more distinguishable.

If you're lacking skill and therefore need a very powerful party be aware that multiclass fighter/thieves are better than dualclassed ones and the extra weapon proficiency and hitpoints for reaching level 3 will help.

Your party is too strong. You can finish the game with half of that party. I am saying this to warn you that it will diminish the fun you are receiving from the game.