
hogarth |

Our group is halfway through the first adventure with a similar party (paladin, cleric, sorcerer/rogue, alchemist) and we're doing very well. The alchemist's ability to add her Int bonus to holy water damage is especially useful.
Of course, a cleric would probably help your group, but I don't think it's essential.

Kydeem de'Morcaine |

Our GM has modified it, so I can't be sure it will apply to you.
But we found that a paladin could not keep up on removing all the ability drains, diseases, and poisons that all the undead dish out. And there wasn't enough loot or purchaseable items that would take care of it available. IF you allow the PC to purchase more or up the amount found as loot it would be ok.