I suppose it's the usual problem that the game designers wanted to make the game as flexible as possible. So you don't have to have a balanced party to beat it. Bioware knew that we would want to do crazy things like solo the game, so they made is possible for us to win with just about any party. If they hadn't done that, the game would not have a fraction of its replay value and we would not be playing it so much!
This meant that the game designers had to put in goodies for parties that didn't have a particular character, a healer, a thief, or whatever.
No fighter? Use summons - horn of valhalla, spider figurine, mage or cleric spells. Or strength potions. Or Tensers.
No thief? Clerics can detect traps. Knock or high strength can unlock doors and chests. Potions and staff of magi for invisibility.
No cleric? Get healing from temples. Ring of regeneration, cloak of the sewers. Healing potions. There have to be plenty of these lying around. Otherwise solo fighters and groups without healers would have to cart around a vast amount of potions.
No mage? Use wands or the magic ability from weapons, rings, etc. Identify with the glasses of identification (cheesiest item in the game, if you ask me).
Bioware also didn’t want you to get stuck in a dead end. So they made sure that there is nearly always a way to beat any problem. Sure, it gets a bit artificial when you just know that a potion, ring or weapon has been put there by a game designer to make life easier for you. It does damage the realism a bit. But I'm sure we can live with it.
My solo berserker (modelled on Korgan) currently drinks potions like a fish. And he has the glasses of identification in his back pocket. But he gets fed up with all these stupid scrolls and stuff that he keeps finding, but can't read. Now, my other solo character, an Aerie look-alike, is the opposite. She hardly uses potions, but loves the free experience she gets from reading scrolls. And of course she has the identify spell and so didn’t bother with those silly glasses.
That's the beauty of the game - there are so many ways to play it.