You'd definetely be needing a thief early on, but around midway to late
SoA they'd become more a luxury than a necessity depending on how much you're planning on accomplishing.
Cernd's werewolf ability would be invaluable for those critical points, best to have him more often in the supporting role though rather than Jaheira, as his accuracy doesn't tend to be as good as hers except when morphed.
I'd suggest also having someone with a berserk ability nearby if you have any intention of ticking off mages who have spells going way before your druids can get their insects away - especially considering some mage spells used by the Cowled Wizards for example make it a living hell for insects to chew through.
Often I find the first Irenicus fight to be rather easy (if without enhancement) without a mage or breach spell. But since enemies do get tougher as the party does, best to always be prepared for the worst eh?
If otherwise; Keldorn's special Inquisitor abilities should do the job, especially since most mages like to be invisible, as well as thieves - but they tend to nullify that ability's effectivness for some reason.
Classic Adventures - a Total Conversion compilation dedicated to bringing many of the old and new PnP modules into the wonderfully dangerous world that is Baldur's Gate II. Fancy link button to Downloads page.
CA Forum. Bugs to be squashed, feedback to be welcomed!
Website at: http://classicadventuresmod.com/
~***~***~***~
When in doubt, lockpick a mudcrab!
Beware the nug conspiracy!