Enter1ch: After realising that Yeslick and Coran are available so late ( act 4 cloakwoods ) i changed my party a bit, but im not 100% happy with that constelation ^^
Actualy im using:
PC Fighter/Illu dual wilding long swords.
Imeon ( no more dualing her i think, using short bow )
Khalid ( longbow ) will be changed to coran later on.
Kivan ( composite bow )
Neera
Jaheira ( will be changed so yeslick later on , i think its a great tank with good heal/support spells , but so late...)
Im not sure about Jaheira.. i used Branwen a bit: she got pretty low dex/con to tank the stuff but she got much more usefull spells then Jaheira.
Jaheira on the other side... she is not very usefull because she cant use proper weapons ( only that damn staffs... ) and no shields at all. But atleast she can take some hits and is able to heal.
I suggest putting Khalid and/or maybe your PC up front with the heaviest armor they can wear and a shield (extra AC) for tanking duty. Put both up front early, kiting enemies as needed when hp on one of them gets low. You can drop it to a single tank for generic work later, after they've gotten some levels (make sure to have one or two people ready to step in front of other party members in case you get surrounded or something). I'd imagine Yeslick can step straight into an off-tank role once you acquire him; the biggest issue with Yeslick being a main tank is that if he gets hit while casting, he'll lose the (healing?) spell, and you want most enemies swinging at your main tank.
After your PC gets some levels (and necessary proficiencies for dual wielding), he can drop the shield for a second sword. Some spells can help make up for not using the shield.
Other than that, just keep in mind that Khalid and Jaheira are a pair. Unless one dies (or you mess around with area changes), they are going to leave at the same time. Plan accordingly when deciding to pick up Coran and Yeslick.
Jaheria vs Branwen: I seem to recall that both can use shields, single handed weapons (a few), and a sling. I wouldn't make either one a primary tank, though either could hold the line in a pinch to keep mooks off Imoen and Neera (or all your other fighters are too banged up to risk). Slap a 2h weapon and some decent armor on Kivan and have him step up before your cleric does; Kivan getting hit won't cause the cleric to lose a healing spell.
Ajantis or Kagain can easily tank for you in place of Khalid, with the choice depending on preference and how you manage your reputation.