The campaign is not a low level only campaign like ToEE or Pool of Radiance.
Mantises deal 27 hits per round or something like that by the end of the game (and note that a non-mantis warrior with a good two-handed vorpal weapon will deal as many damages), obviously it's a game where you're meant to do crazy things. And if the player is the only one who's doing crazy things but enemies don't then it's boring, total symmetry is not needed but at least some illusion of some sort of symmetry is good. In Pools of Darkness or Dark Queen of Krynn you'd better win initiative or you'll get killed, more than the previous games in the series because of a different ratio of fights which are trading blows (kobolds, goblins, gnolls, bandits ... while in later games it would be the occasionnal fight againt othyugs or such, ogre clerics won't be kind) but if you tell me you never lost an early fight simply from one or two clerics succeeding in casting Hold person then I'll be very skeptical.
I think that the variance was indeed taken a bit higher, like
Darth Roxor said if a dark mage wins initiative then your entire party is killed (like in Wizardry, by the way) while only one Rakshasa alone would only cast a fireball and it would take more than one to kill your entire party. However if we're specifically talking about the little fights against one of those mages and several irrelevant thugs (these fights suck, because there's no real tactics, while the ones with plenty of mages and other enemies are fine, and very fun, and the last fortress would be totally anticlimatic if it would not feature such kind of battles in this such game), these battles occur during the last parts of the game, when the initiative of your mages is high enough at this point that if you have at least two mages it's very likely one of the two will play before the enemy mage, you will rarely have to reload in all those trash fights against one mage and thugs, and such a fight will take you 5 minutes at very most, it's not the meat of the game. People are talking as the game is easy but you need to reload a not (I'm exaggerating on purpose), but in my opinion it's not and the variance is not higher than in other games in the proportions that people seem to imply, in my opinion the reason why you need to reload a lot is because it's hard (and the system is what it is), the average difficulty of the game is probably the average difficulty of the only ten hardest fights of KOTC1 or Pools of Darkness, no way I would have won the boss fight against many giants in KOTC1 with bad initiative. Of course ultimately you reload a lot in KOTC2, not because overall the encounters are more dumb than in other games with similar systems, they are mostly harder than in other games with similar systems. If you intend to win the game with a barely average party and without paying much attention to combat tactics I just can't imagine how much you're actually going to reload.
I never faced a encounter in a PnP session as hard as most of the encounters in KOTC2 but I never faced an encounter as hard as the one in the big room with giants in KOTC1 so I can get the point but I would not call that a totally fair argument anyway. Save systems are a very complicated, very controversial and very interesting topic, and my opinion is that if the game has a permissive save system then you design the game acknowledging there's a permissive save system, you don't have to agree with that but of course if you don't then you're not going to like the game, but then I feel like you can't like even KOTC1 either.
I know people hate the game for many reasons combined together, I never defended skeleton warriors with +5 weapons and you get nothing after the fight, I never defended the actual look of the game (tokens are fine, the actual tokens are awful) but I have no problem defending the encounter design, I really think the encounters are harder than stupid (stupid because of reasons which would have nothing to do with difficulty). If anything the encounters in Wizardry are both much easier and much more stupid.
The small retarded encounters could be redesigned but they are not the ones where I reloaded the most, the encounters where I reloaded the most are more than often the best ones, either against cool gangs of enemies (gangs of undead especially, or these mind flayers), or the ones against big groups of enemies which are totally fine and the very best ones in the game. The Spider Queen is a bit bullshit but isolating the very hardest, optional battle, would be dishonest. Pizzara, the witches, the battles inside the fortress, I loved these ones.
I like that the game is hard and I like that the system is crazy, if I need to reload more because of that then I don't mind.