(be prepared for yet another long long opinionated essay... because work is boring)
I think in the cases of both the Undead Slayer/Pale Master and the Assassain/Paladin, those characters should be made to smite themselves into oblivion. If a paladin truly wanted to become something extreme like an assassain, he should go through a total rebuild and have those paladin levels stripped for something more appropriate, like rogue or fighter/Blackguard. Fallen Paladins should not get to retain their fear immunity and charisma bonuses granted by their gods... Faith and god gave them these abilities, and thus they should waver along with the faith. You can say "oh well they can't use their abilities like spells and turning" but that's not enough IMO. Because if given the chance, how many of our other characters would take the feat "Immunity: Fear" or "Charismatic Saving Throws"? MOST of us would at least take one.
Other NWN class combos that make me cringe from their sheer illogic are the Dwarven Defender/Rogue (dirty sneak attacks, sneaking and lockpicking are NOT honorable, any way you slice it) Rogue/Paladin (even worse!), Aeridenites who take improved crit which only hurts the living, Druid/Wizards who use huge fire spells while in the woods (Ones who use smarter spells are ok), Dragon Disciple Pale Masters, and other such cheesefactor combos.
I am however sad that we have the restrictions on monk and druid multiclassing, since there are a whole lot of classic fantasy archetypes which fall under those classes being supported by multiclassing. Take for example, the Monk/Sorcerer. Brilliant! Leap around hasted and fighting unarmed, shooting fireballs from your fists like a mystical martial arts wujen. Then druid/cleric/undead hunter... how can you get any more aligned with nature than that? You get to preach the word and live it too. Druid/monk for those who want to specialize in animal-based martial arts like Leaping Tiger, Monkey Style, Praying Mantis, etc. Druid/Rogue for truly sneaky and elusive druids that like to blend into the forrests and sneak attack somebody as the bunny from Monty Python. A Monk/Dwarven Defender would be the ultimate sumo wrestler! Big fat naked dwarf just sits there and squats, YOU CANT MOVE HIM!
Technically you can make such combos, but you never get to train them in a manner that doesn't stunt their development, and effectively make them one class or the other while abandoning most of what they learned before. For these reasons above, is why I have always yearned for the skill-based system being implimented in the next version. It's just too restrictive to think of all these different skills in terms of classes, and we'll finally get to pick and choose how our character will be... unarmed fighting druids, Dragonball Z flamethrowing monks, martial artists that study dodging, unarmed and weaponfighting but don't care at all about spiritual development, shapeshifting assassains, etc.
Meanwhile we unfortunately have to work with these chains D&D and Bioware put on us. For example, MOST of the social skills are only in rogue and bard classes. NWN actually has the audacity to suggest that if you have social skills, you are by virtue an unlawful person who sings and stabs people in the back. (my main pet peave with D&D! "I have heavy armor so therefore I am a social pariah")
I do like the loving that Lucindite Paladins get when crossclassing freely with wizard classes, just it doesn't make much sense to me why they couldn't do so with sorceror classes. If anything, a sorceror would be more devout than a wizard in my opinion; Lucinda gave them their powers, in a sense. Sorcerors should above all feel that they are the champions of Lucinda, in my opinion. She "chose" them.
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On another note touched upon by Barion, I am of the firm personal belief that polytheism and practice of multiple religions should be supported. There aren't that many true atheists in a world where prayers are answered before your very eyes, so Monotheism is somewhat moot in the sense of being the belief in just one. Even our own gods warn us of other gods in the scripture, I'm almost certain there would be at least some mention of Pyrtechon in Rofirien's scriptures as being the enemy to be thwarted. On that note, the gods themselves have vastly different portfolios which just don't make sense to pray to them for certain things. You wouldn't pray to Dorand at sea unless you were specifically praying that the shipbuilder's knew their craft, but rather you'd pray to Mist or Katia to quell the storm or Shindaleria to steer the ocean currents. Why would one pray to anyone other than Deliar when betting on a horserace? (ok, maybe to Kitharian to gift the horse with the fleet of hoof, lol) Further, the gods have a very concrete set of alliances between other faiths.
Mechanically, when a cleric raises a follower of another god, his own god will treat them as if they were of the priests own faith if the two deities are the strongest of Allies. (no xp loss for allied raising) In that sense, there's almost a selection of heavenly and hellish "teams" of gods competing and conspiring against one another, in such a manner that many of the gods have a lot of goals in common... "heresy" wouldn't be an issue between them I think. The "all-or-nothing" method of faith is too simplistic for me in a world of godly alliances. One does not praise Thor with one breath and slander Odin with the other, any more that they would follow Rofirien's laws and not call upon Toran for protection of the law. In most of the major pantheons in history, there have been allied faiths and people who follow more than one god, priests of the gods being the only typical exception.
So the common FAITHFUL follower would visit the temples of the gods he liked and avoid the ones he didn't. This whole reflexive response "if you worship more than one, then you're obviously not devout enough to have a diety in your field so make it blank" is both historically inacurrate and illogical to me, and seems more in line with OOC western monotheistic thought than IC devotion. Why would somebody attend temple to both Zeus and his wife Hera and a few other gods if he wasn't devoted to them all? When gods like Prunilla and Deliar are married, wouldn't it be an insult to Deliar NOT to pray to his wife in homage to bless your family? That's just my opinion of course, and the fact of the matter is that the gods have the power to be as jealous and fanatical as they choose to be.
