Ah, so if you visit it late, it is a bit too easy. If you visit and finish earlier, the original end-game becomes too easy? Is that it?
Exactly. The game offers you the option to increase the difficulty of the game if you are considered too high level but I found it is not enough and from what I have read many people concur.
But I understand it's hard to do. I am not sure I have played RPG which had expansion accessible during the main story and not making any part of it unbalanced.
It is price one has to pay for it but I personally think it is worth it.
If you are going to stick with it I think best time go play expansion 1 before visiting Twin Elms (it is quite obvious in main story) and I am still not sure where to do part II. I once did it right afetr 1 and it was quite hard and then rest of game was just walk in the park and second time I did it just before the very end of the main story and it was a bit on easy side but overall better I think.
Heh, this is so true for many expansions to RPGs. Saving Icewind Dale from the greatest evil ever? Well, that can be put on hold while you go on the expansion quest.
Thanks to everyone for your answers.
Well, the part II presents maybe the bigger threat to game world than main story so it quite justifiable to make a detour to take care of it.