Ranger19k
Explorer
Swift Hunters can use skirmish on their favored enemies even if they are immune to precision damage... but with only 3 levels in Ranger he only gets 1 favored enemy, which is why Swift Hunter builds tend to have more Ranger levels.
I don't disagree with Dandu's points, but the Swift Hunter feat stacks Ranger and Scout levels for the sake of determining Favored Enemy as well as skirmish damage, so this character will actually have 3 Favored Enemies. If he took all precision damage resistant creatures (a smart thing to do), this will limit your options a bit more when it comes time for determining what to throw at them that will be precision damage proof, but like Dandu pointed out, there are at least 6 or so types of creatures that are immune to precision damage, so even if your Swift Hunter chose three of them, that still leaves three or so others that he really sucks against.
I would note that Fharlanghn offers no domain power that allows for a move action as a swift action. His domains are Balance, Celerity, Luck, Portal, Protection, Travel, Weather......
So I would start to scrutinize these min/maxers a little bit more.
I actually suspect that he took Fharlanghn's Travel domain, and then swapped it with the Complete Champion Travel Devotion Feat which does give movement as a swift action. This is a pretty standard swift hunter tactic. Aboyd makes a lot of good points, so I'm not mentioning this to disparage his comments, but rather just to caution being careful when scrutinizing the player's characters. Nothing wrong with taking a hard look, but their builds look legal to me, so I just didn't want you starting the conversation with accusing one of them of doing something illegal when it probably isn't. It's all about conflict management.
Anyways, all of these guys have given some pretty solid advice. I would simply reinforce the notion that as DM, you are not required to allow ambiguous interpretations of the rules or access to all the splatbooks. Even if CharOp says that it's legal by RAW, if you think it's too overpowered, you can always swing the "overpowered nerf" hammer. It sounds like you'd rather not do this, which is fine, but I agree with Eldrich-Lord that the Kaorti-resin does not need to be available for easy purchase.
Maybe make sure that the min/maxers can give a GOOD Role Playing explanation for why they have such equipment and how their characters developed the way they did. If the explanation is no good, then feel free to have them adjust a little. Nothing major, but small fixes might make the difference.
Otherwise, yeah, maybe help the wizard improve his tactics/spell selection a bit so that he can contribute more in combat.