Cone of Cold will bypass all Dark Wizard protection, and if they fail the save, wonderful things happen (like 400+ damage; this can also happen to Enchanted Bozaks).
PWK works because Dark Wizard HP is garbage at any difficulty level. It has the advantage over Cone of Cold of being instant cast.
For some reason I had missed the usefulness of PWK. I'll have to look at that.
Dark Wizard has 56 HP in Champion difficulty. Low enough for PWK of course. With that HP, typically from lower level mages, even two cone of colds couldn't kill it (but you could maybe finish it with missiles; again, to get through protections you might need to launch two or three volleys of them.
You had a few problems that was due to you misunderstanding what was going on.The most obvious one is your idea that Dark Wizards are harder at higher difficulties. They are not (other than the extra HP). The issue with Dark Wizards is the Fireshield (Cold) that they have on (Enchanted Bozaks has the same), which makes any fire-based attack 90-99% ineffective even on the middle difficulty. This includes DBF and Meteor Swarm. You need to hit them with Power Word Kill or Cone of Cold. This has always been the case regardless of difficulty.
I somewhat doubt if that is really the full story. At least according to the manual, if the enemy has fire shield (cold), you should be able to deal half damage with DBF if the opponent fails the saving throw (improved by 2). According to
https://gbc.zorbus.net/mm/07_tdqok.html , dark wizards (with Veteran difficulty) have a saving throw of 6 against spells, so +2 means 4. This would imply that 1/5 of the time (so 20% of attempts) you could breach the dark wizard protection with DBF and deal damage. But I don't think it never happened with me with Champion. So there is likely something else going on. On the other hand, you certainly could breach the protection of enchanted bozaks with DBF sometimes but rather rarely, if you overcome the magic resistance and the bozak fails the saving throw (its base value is 10, so 8). The easy explanation would be if the saving throws were also adjusted based on difficulty (say, if in champions difficulty enemies would get +2 bonus to the base stats that would mean dark wizards would always succeed in saving throws and would never get damage).
I would be interested in seeing if someone has decompiled the games and/or otherwise can precisely tell what's going on and what the difficulty levels actually do.
I think the issue with meteor swarms is different. At least in classic D&D, IIRC, meteor swarms cause both concussion damage (while flying to everyone in the path) and the explosion damage when they hit the target. I think only the latter is fire damage. If that is true, fire shield (cold) would not protect from the former. I think that would easily explain why you are able to get some minor damage out of meteor swarms on enemies which have fire shield (cold) yet apparently not so with DBF.
The go-to option against Beholders has always been multiple arrows to the face. They are slow (speed 3), and their rays have limited range. It would be a go-to option against Fireshielded opponents as well, except those also tend to come with Protection From Normal Missiles as standard. You need to use magic arrows against those (Dark Wizards also have Mirror Image up; which is why Cone of Cold is a better option).
Good hint. Unfortunately in many cases beholders are spawned in close quarters and it may be very difficult to escape the range of their rays. And with 120 HP, they take quite a beating even from seasoned fighters or missiles especially if you are not hasted. In typical encounters there were usually at least 3-4 beholders in different locations. All in all, you need to be somewhat lucky to make saving throws against disintegration and death rays, so more reloading etc.
Also, you can rest straight after you escaped from the Abyss. In fact, I believe the game actually tells you to. The egg only starts hatching when you examine it.
No, if you try to fix/rest, you are interrupted immediately and the egg starts cracking. The same if you move a square. All you can do is cast healing and preparatory spells in the square you arrived. Again, this would likely not have been such a big issue if I had just been prepared enough, i.e. two batches of prep spells, first in the abyss anti-magic battle and the next for the chromatic dragon. (Obviously, still luck would have been required to avoid someone getting killed; at least in champion, the computer seemed to get initiative almost always and some heads were also guarding and hit you immediately when approaching, thus reducing significantly the damage output of two dragonlances.)
Your other problem is that you did a run with way too many triple class characters. Unless you are willing to run through DKK multiple times to get enough XP to get all triple class characters to go to level 16, don't take any triple class characters. Dual class is absolute maximum. For a straight run with no repeats:
Human Knight (Sword when you max out levels in COK and can convert without dropping levels; Rose when you can be level 18 Rose after changing)
QElf Fighter/Cleric of Kiri-Jolith - Detect Magic (you can never have enough) and -1 THAC0 (coupled with elf -1 THAC0 bonus with swords and bows is massive in COK)
QElf Fighter/Mage (Red) - Red Mages have a number of self-only buff spells that are paradoxically useful for Fighter types, not Mages
QElf Fighter/Mage (Red)
QElf Thief/Mage (Red) (only if you want to do Dave's Challenge in DKK; otherwise use Human Mage (White) or another QElf Fighter/Mage (Red))
Human Mage (White) - Power Word Kill makes your life a whole lot easier; get it ASAP
I agree. I was afraid of hitting L14 level caps too soon (compare to POD where characters reach much higher levels and get more XP), but it was the opposite; I guess with dual F/M or F/C I could have obtained L14 just nicely before the game started getting much more difficult towards the end.
I wonder if having only one half-cleric (plus a knight at some point) might cause some issues later on, especially if it would get knocked out. But I suppose it would be interesting to test this "mage-maximised" setup.
Why human mages? Elves have better dex so better initiative, and you can do a lot of haste spells without much concern (I wonder when characters die of old age if not given elixir of youth?). Of course they can't be resurrected but I wonder if you want the reduced constitution anyway.
Remember that Turn Undead, while useful, lowers or completely eliminates the XP you get from the encounter. Don't bother unless absolutely necessary. This makes Majere clerics less appealing.
The annoyance in DKK was a huge number of level draining undead, starting from lower tiers such as wights and spectres that you could turn. When you don't have access to restoration, getting a hit could mean running back to the closest city. Isn't this a problem?
By the way, I wonder how the XP mechanism has been implemented while you're level drained. In original D&D, I think you get restored to the minimum XP of your original level so level drain always led to losing lots of XP. But it seems gold box games are different. If you gain XP while having been level-drained and then get restored, it seems as if you get back your original XP (but I didn't check, not the minimum in any case), but do you also get "full refund" of the experience you gained while being drained? If no XP is lost, of course then running back to get restored would not be such a big problem.
Ranger/Clerics are traps. I learnt that really early back in the 90s when I first started playing DQK. My very first DQK party had a Ranger/Cleric and I couldn't figure out why the damned thing never leveled up. Even the Rose Knight was leveling faster than him. Then, I looked at the XP tables and facepalmed.
Further, I read somewhere that there is a bug in DQK where you lose XP when training ranger/clerics. I did notice something odd (I could train the character one time and immediately again afterwards), but did not investigate it myself.