I would dump Jaheira for Nalia! Why? I am so glad you asked
You have a good bunch of fighters so no need for any more. While Jaheira has some good healing spells, these are easily made up for with Minsc/Aerie/potions/ring of regeneration. Nalia adds another mage to the mix, which I think is very important to back up your tanks.
So IMHO dump Jaheira, add Nalia and kick ass!
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