I agree with both of you, actually.
But it's not about a game being designed for non-optimal characters, it's that optimal characters are FUN to make, if you're into that sort of thing.
Obviously, the issue is that we're too aware of what goes on behind the scenes, and the fact that we're privvy to information that used to be for the developers only.
These days, the players know more about the game than the designers do, because the designers deal with theory more than practice.
Games like WoW and Diablo 2 - showed us that as great as those games were, they were never balanced properly, and they never will be. Players will always figure out the loopholes and the exploits - because there are millions of them, and they're sharing information about a game they're playing for hours every single day.
So, droplists and theorycrafting means it's an incredibly hard job for a developer/designer to balance loot - but I personally think it can be done, and I know how I would do it.
You need to combine the element of suprise, with certain assured rewards - but you also need to understand your own game. As Maylander says, Diablo and Baldur's Gate are vastly different games, because the first is meant for indefinite replays and the latter is basically a one-time thing, with a much stronger focus on the story.
But both games lend themselves well to min-max'ing - and players will want to know how powerful they can become, and they will want the best loot. That's just a kind of player that will always be around, and you can count myself among them.
It's not enough to handplace loot in a game like BG - because even upon the first playthrough of the game - it will mean you have to wait with the most powerful stuff towards the end. The thing is, though, that when you're building a powerful character - you want to enjoy him for large parts of the game. You don't want to make the player wait until the end-game with giving him the good stuff, he has to have a chance at finding it during the earlier stages. That's where random loot can be helpful to a designer, because even if the player finds a powerful item - there's always going to be the chance of more power, later on. A typical mistake is that designers think all battles must be challenging, and they forget that there are different kinds of challenges - even within battles. Players that focus on creating powerful characters and work hard on that, should be rewarded by BEING powerful - at least to a certain extent.
What you want to do, though, is ENSURE that the handplaced loot is unique and has certain powers that can't be had with random loot. Not necessarily MORE powerful, just unique.
That's a mistake I've seen in Diablo and other games of a similar nature, where even unique items have some limited random stats - which, to me, works AGAINST the idea of unique items. I'm a huge fan of items having lore, and a reason for being where they are. The more backdrop, the cooler the item. Sometimes even a less powerful item is cooler, just because it's so steeped in lore.
Balancing power for random loot and handplaced loot, is very hard - but it's about the underlying system and your own understanding of it, as a designer. If you don't understand your system in-depth, you're going to be placing loot where it shouldn't be. People tend to forget this, but balance in general is probably THE hardest part of any design, especially in a competitive game. It seems to me that most game designers today, even the best ones, just don't focus enough on their systems and they tend to downplay what it means to not fully comprehend what outcomes there can be.
Either that, or they go the Bioware route and simplify everything, because they don't WANT to deal with complexity. That's even worse.
That's not so bad in a singleplayer game, but in a competitive environment like an MMO, I don't understand why they're not focusing on these things in a much bigger way - but then again, there's a huge disparity between actual balance and perceived balance
Loot design in MMOs is so horribly bad, and it's like they either choose between boring loot where loot doesn't matter, and loot being the driving force behind the entire game - meaning players need to grind eternally for it. I like LOTRO's idea of the legendary loot that slowly builds in power, but I think the implementation is flawed - and the game is boring in terms of combat, anyway. Loot should be available to everyone willing to work at getting it, but for heaven's sake don't make it like a real job. Then again, MMOs are so stagnant in terms of design, I could go on for ages.
But I digress.
In any kind of CRPG - I want the combination of random loot and handplaced loot. Handplaced loot, not so much for power, but to give the player a sensation of history and immersion. Loot should be placed in a reasonably logical fashion, and I don't want rats dropping swords. I don't fret about such things, but it would be nice if everything made sense.
It would be perfect if they could make ENOUGH handplaced encounters with handplaced loot, to make the game eternally fresh. But that's not feasible - especially not in a game like Diablo. So in such a game, random loot probably needs to be there. In a storybased game, handplaced loot can suffice - but I personally prefer having a chance of finding stuff that I can't predict, and that I can't plan ahead for. I also think it keeps the game fresh, and even story-focused games can be replayed numerous times.
But in the end, I don't think of this as much as random vs fixed, but about the implementation of said systems. Random loot isn't working if all you find is worthless junk. Diablo 2 was really bad in that way - in my opinion - but that's probably because it was designed as a multiplayer experience - and on Battle.net you were meant to trade for stuff. That's great, but not if you're playing alone endlessly to find something you can use. That's when you need to understand your game, and you need to give your player an opportunity to work towards powerful loot - if he can't find it at random.
But if you craft your system intelligently, and ensure it remains relatively opaque to most players, you CAN make random loot work and make it truly exciting. All that is about balance and what kind of experience you want to give the player. But I think it's best to give them the opportunity to work towards power when random stuff isn't cutting it. Crafting, being an obvious way.
When going the 100% fixed route, I suppose it's really about taking every single build into consideration, and on top of that - you need to make the game flow. If you hide the good stuff until the end, people will miss the experience of being powerful - and it's my opinion that they need to get that experience in the middle stages, at the latest. It's no good having only a single truly powerful Katana and then letting it be in a chest during the very end game. That's stupid. So, not only do you need plenty of diversity, you also need that diversity to be apparent THROUGHOUT the game, and that's a lot of work - if you want fixed loot to make sense. That means hundreds of meaningful encounters - and designing them is HARD work. That's why I think random loot can be very helpful, even in a story-oriented game like BG and its ilk.