The elementals - I believe you need to use a freedom scroll in the trapped wizard cavern.

A powergamed party:

Viconia (is there anything that 50% magic resistance can't do)
Korgan (Berserk and dangerous)
Nalia/Imoen (enough thief to do most things thiefy and enough mage to do anything magey)
Mazzy or Minsc (I just don't like Valygar, Mazzy would probably be my preference of the two)
Usually I'd throw in Edwin too.

I wish there was a way to keep Yoshimo. A dualled Yoshimo Thief/Fighter can be awesome.

Optimally, you'd have Keldorn too, but he and Viconia don't go together all that well.

I tried soloing the game with a swashbuckler recently. Worked out pretty well, but TOB got a lot harder. Couldn't finish it because computer died. Generally, the way to deal with dragons is to spam protective and benefit spells before trying desperately to smite them with massive damage.