I've just found the article now, and yeah, you are right. Tyranids are pretty much controlled by AI, it also mentions they'll surround player territories and attack them when they are vulnerable. It doesn't mention more detail then that.

"Because you have a few continents on the planet, and each continent is split between all of the different factions at the start of a campaign. However, each of these faction areas are surrounded by Tyranid territory, and the Tyranids will be controlled by the AI."

"They will always try to eat away some of your territory, and if you’re on the war council or in a strike force, you have to make sure that if you push for battle to take territory from the Eldar, you’re not leaving your rear to the Tyranids, because they’re going to eat you from behind while you think you’re winning the war. So you have to manage that. The Tyranids will stay away from large battles, because adding NPCs on top of players in a large battle will create performance issues. Then again, the Tyranids would wait for a battle to finish."

How about we let the Ultrasmurfs handle the 'Nids. They like doing that, I hear.

I would love some good PvE content to take on with my friends. I hope we will be able to fight gene stealers, termagonts, hormagonts,and even a tyranofex or two to fight with my friends. (sorry if I spelled the names wrong)

Hope to see big swarms of nids.....so you get the feel you're toasted and just try to survive that slaughter.

Indeed, like the Gretchins in Space marine, you want to feel powerful gunning them down / blowing them up.

I like the idea of AI Tyranids being an ever-growing threat. Just imagine, you can't claim an enemy territory, so you infiltrate in and sabotage their efforts to halt the growing Tyranid infestation. If you can't have that territory, then nobody will!

I think if the are smart they will look to DoW II on how to proceed with the Nid PvE, that wouldn't dillute the PVP aspect which is a concern.