Duke deployment

I am considering adding the duke to my Wych cult army list, but his "deploying in the warriors/trueborn" rule confuses me. If I do not have a unit of warriors or trueborn in my list, can I not take the duke?

Yes you can, but you can deploy him anywhere, following standard deployment rules.

Yup, it was in the FAQ.
You will waste the poison rule, but he can be deployed anyway in any unit.

Would you recommend taking the duke with a squad of warriors in a raider and get the duke to tag along with the wyches when an opportunity arises? Or should I drop the duke in favor of a subbubus/archon. I do plan on taking lots of wyches to utilize the drugs but is it worth it to waste the poison/ risk the duke getting caught where he doesn't belong (shooting)?

Remember this: a unit can be deployed outside its dedicated transport. Duke could be deployed with a unit of Kabalites, next to a unit of Wyches. Both units are deployed outside their respective transports.

Duke switches units, both board their gunboats, and off you go.

Also, it's not like the poison rule is all that mind blowing - and Duke partners quite well with Wyches since he wants to be in assault anyway. If your list doesn't have Warriors/Trueborn I wouldn't bother changing it to include some just for the Duke, he's still pretty amazing for you if you have a lot of Wyches because that re-roll is amazing.

Similar to DingK, another option is to put a squad of warriors in ruins, on an object, etc as a fire base in cover. Start the duke with them and just leave them there. Anything that comes close dies and it is fairly cheap. Though a 60 point DL raider is a good deal.