Arthandas: There is no roleplaying in IWD and you don't lose high level casting options. The game is also not balanced specifically for single class characters because it faithfully follows 2nd Ad&D rules.
IWD is a rpg and there and there is of course a lot of roleplaying for you to have if you're interested. I replayed with a party consisting only of pregenerated characters (there's no pregenerated multiclass for using at the start of the game) and it felt different.
Arthandas: But enough for most double multiclasses which further proves my point.
If your point was "multiclassing is more powerful than single class for some classes if you cheat up your XP so you always play with the amount you would have after playing your characters through both normal and HoF mode" then yes.
But I don't think this was your point.
Arthandas: Yeah but 30 mage would be obliterated by 20 triple class who has only slightly weaker spells but about 50% more hp and cleric spells.
Maybe in a solo game but not in a party with different roles.
Arthandas: Also, stop saying that multiclassers advance slower because they don't. Their advance is slower only if you look at a single class and forget they have 1/2 more. When your single class fighter gets 10000xp, your multiclasser gets the same amount, it's just distributed differently.
Sorry, I didn't know about this fetish of yours to press artificial misunderstandings into words where it's obvious how they are meant and get hurt.