I see everything as a balance of Yin and Yang... in Nightmist, it is a balance of attacking and defending/supporting...
Classes such as Fighters, Berserkers and Rangers are very Yang... they are primarily frontal attackers with not much regard to their own well-being - against a tough opponent, namely a boss, they will not last long once the potions they carry are depleted; while Clerics and Pacifists are very Yin... they can take care of their health and the health of others with relative ease, but are not very good attackers and once again, will not generally survive an encounter with a boss because they cannot do enough damage (except versus the undead, but they're strange!)
To make a good alt team, you need to balance out Yin and Yang, namely by having a Cleric supporting your attackers; and when you add more attackers to your group, you may find you need a 2nd or 3rd Cleric to cope with the healing, so your group does not become too Yang.
Paladins, on the other hand, are quite well balanced in Yin and Yang. Their attacking skill is moderately good, and is balanced with moderately good healing spells. This generally means that Paladins are very good when used by themselves, but when it comes to a team of alts, Paladins are not particularly strong attackers when compared to Berserkers and such, and if you don't use the Paladin to heal him/herself (which most people don't; they use a Cleric), it does not make a good contribution to the team.
The Yin/Yang balance is quite well centralised with Paladins, but putting them with other classes in a team of alts tends to unbalance them, and trying to strengthen both sides of the Paladin, to make it stronger but keep the balance, will make them too overly powerful versus the other classes.
That probably makes no sense whatsoever, but that is one way I have looked at it and have attempted to translate into plain English.
P.S. If you are not sure what Yin and Yang is, it is symbolised by this quite a lot and is the basis of almost all Oriental medicine, martial arts, food and mythology:
