As Maduro said, it's important with the final tier of Ixali quests to only craft 1 thing at a time because, depending on the specific quest, there are up to 3 different debuffs that you can get (all previous tiers have the same debuff for every quest). They're -150 CP, -50% CP, and no cross class skills. With all 3 stacked I don't think anybody can really complete those effectively since you'd have maybe 100 CP (and no CC skills).
I personally prefer WVR to complete the quests because of CS2. When doing these for exp, it's best to get at least 1 class up to 50 so that you can more easily finish the higher tier quests (I imagine they can be difficult for low level crafters) and grant more exp to whatever crafting classes you want (and collect oaknots).
EDIT: @ Mishini: None of the quests inflict more than 1 debuff. All of the gathering quests reduce your CP (I forget if it's 50% or -150 -- nearly the same thing) but are easy to complete anyway. If you have reduced CP and no access to CC skills then you've activated 2 or 3 quests at once. You don't ever have to deal with no CC and reduced CP simultaneously.
You don't have to. Left click on the debuff that's not related to the synth you're working on. If you don't know which is which, just remove both debuffs and talk to the NPC again to get the correct one reapplied.
