Took me some time to figure this one out.
I have searched through the main six books of Dune story and have found that author carefully evades any mention of the weaponry save the knives and laser pistols. This does not, however, prove either point of view. On the other hand, there are many indirectly mentioned "heavy arms", "heavy weapons" and so on. I cannon provide you with exact citations, since I only found russian translation online (which allowed me to search, not read through the books), but there were pointings to light and heavy armored vehicles, walkers (like AT-ST from Star Wars), both laser and projectile weapons. I would also like to mention that there was no problem with shifting sands on Arrakis (sands don't shift in such a way that a car cannot ride upon it), but the vibration that attracted worms that simply ate the machinery
Having said all that I think there is no problem with tanks and artillery in Dune universe. The books focus their attention on politics, philosophy and religion, it's not some kind of an action story, although it may, at times, feel like one.
There is one thing although, that is generally mentioned almost in any book. It's the prohibition of atomic/nuclear weapons. That's probably why Harkonnens had it
Concluding the thought - author did not elaborate on weapons used during massive battles (probably for a reason) because it was not his point of interest. Therefore we are free to imagine anything we want. So basically if we want to stick to one era scenario - whatever we can use from Dune2/Dune2000/Emperor games is okay. If we want a bigger picture then we'll have to invent what Frank Herbert was so carefully avoiding for whole 6 books saga
