I am puzzled that every fighter can use the Dragonlance; I was pretty sure that only knights could wield them in Champions, but maybe that restriction was relaxed or I misremember (I am sure about the solamnic plate, though). Anyway, I think they SHOULD be restricted, IMO, anything else seems out of character with the Krynn world.
Anyway, as one never gets more than one Dragonlance (or can one import one from DoK and get another one in DQoK? I played the latter without transfers), this is a moot point when thinking about the number of knights. I agree that they get some good clerical spells later on. But the Paladin protects a whole battle line with his protection from evil and gets to healing spells earlier (though never as good as high lvl knights). As I said, I think they should have excluded paladins from the Krynn games (as they did in Champions) but with the many undead in Death Knights a paladin would be quite useful there. And there are only two dragon fights in DoK where one could use the lance, I think; one of those is a optional one (Cekos) many players probably do before they get the lance, and the hardest dragon fight comes right before one gets the lance.
When I played Death Knights recently I had: Human Knight, Human Ranger, Kender Cleric/Thief, Elf Cleric/White Mage, Elf Fighter/Red Mage and Halfelf Fighter/Cleric/white mage. Probably because this was roughly the way I had played Champions in 1992 or so. The yelling was much less useful than in Champions (because undead are not affected) but backstabbing is great on skeletals. I am afraid a kender would be wasted in DQoK (but my recollections of that game are dim, I only remember that there are two long stretches where my characters "lost" XP because they could not train in between). It is quite hard and tactically more interesting than PoD, e.g. with the echanted bozaks and auraks (and not so ridiculously long).
Null Null, I am pretty sure that I once played Curse with a party like the one you mention. As one gets Alias and Dragonbait for a longish portion of the game and those are both good/decent fighters such a party should certainly work. I seem to remember that the Half-Elf Ranger/Cleric hit the cap and I thought about having a Fighter/Cleric/Mage instead, get a human ranger instead of the dwarf and make the elf triple as fighter/mage/thief. But then the gap in HP and advancement between the four humans and the two multiclass would probably be considerable. (I probably did this once as well, I think I played the game twice, once on mac, once on pc.)
As for multiple/dual classes I am undecided: Sure, they can get really powerful and some of them make sense to some extent (like fighter/thief); in the case of the elves one could argue that they have some natural magical ability humans lack so fighter/mages are a thing. Otherwise (especially in some Pen&Paper RPGs) one of the main gaming points about mages is that they are physically weak/heavily restricted as bargain for their uncanny powers. And overall, I do not think stuff like an uber-powerful ranger/mage dual does make a lot of sense.
Overall, for immersion and plausibilty I'd probably prefer a system with more classes but no dual/multi at all. So Rangers would be somewhat weaker than fighters but start with druidry or so early on. There would be a bard class instead of mage/thief, paladin would replace all fighter/cleric, a druid would be some kind of mage/cleric etc. But this would be an entirely different system.
Agree about the standard order in PoD. But on my first play I somehow missed Thorne and I think that on one replay I did Kallistes last as you suggest. But the Moander sphere can be pretty nightmarish as well (Tanetal is a piece of cake but his entourage and the random encounters with huge Golems and Moander bits are among the worst in the whole game (especially if one has only one priest and one high lvl mage), there are also some puzzles to be figured out with the blood circulation in the body, without hints one can spent A LOT of time there.)