The fluff on the Asshur from TRO 3060 talks about them being notably used by the Vipers once. A mercenary raid by a mercenary unit called Armstrong's Archers. They tried to raid Graus which was under Viper control in 3054. They faced part of a Phalanx Cluster and a mixed star of 'mechs and vehicles.
The mercs didn't realize one of the vehicles was an Asshur and ignored it, focusing on the 2 Viper 'mechs in the defense. It says the mercenaries' actions freed them from Zellbrigen and the Asshur ran circles around the Inner Sphere 'mechs designating targets for Arrow IV strikes from two vehicles (doesn't state what type) kilometers away from the battle. None of the mercenaries survived.
So, there's another instance where the Vipers used artillery.
It wouldn't surprise me if the Vipers pulled something similar on Jabuka. What I mean is, an initial clash or skirmish where the Spheroids break Zell. The Vipers practically knew it would happen and in fact had made it part of their battle plan, bringing along enough artillery to embark on their chosen strategy. In Clan honor terms that released them from their obligations to Zell and they went ahead with their plan to bombard the Spheroids.
EDIT
It was 1 Clan Galaxy versus 2 dug-in RCTs. This was also later in Revival, not one of the first waves. I can't say I really blame them. But it did surprise me too. I think that because it was a fight versus Spheroids, who by that point it was well understood wouldn't honor Zell, made a big difference in how this was perceived in terms of Clan honor. I suspect around this time (early 3050s) there was this expectation that when fighting Spheroids, they would fight like "barbarians" and so everything was on the table. But what that meant absolutely varied from situation to situation, and Clan to Clan and even just unit commander versus unit commander. The Vipers had a lot of different personalities in charge at this time, Natalie Breen and Christopher Ahmed were very different personality wise than Perigard Zalman for example. That can include battle tactics and what they deemed acceptable under those conditions.
For comparison value... Khan Natasha Kerensky, leading all of the Wolf Alpha Galaxy into invasions late in Operation Revival, found fighting 1 full size good RCT to be a tough fight on Suk II fighting the 33rd Avalon Hussars. According to the Clan Wolf Sourcebook page 68, she knew it would be a tough fight and it was one. On Jabuka it was double that, 2 RCTs.
Another stray thought. The Vipers use fewer ASFs per Cluster (5 to a Star) with more of them assigned as naval escorts, and I believe one of the Alpha Clusters had no air power at all. During Operation Revival we saw many instances where other Clans countered artillery and dug-in positions through heavy use of air power, sending fighters to bomb or strafe Spheroid artillery positions. I think the Bears did this in one of the earliest invasions during Operation Revival. I wonder if having fewer ASFs meant that Viper doctrine saw artillery as more acceptable, since Viper Cluster and Galaxy commanders had less air power to work with. Unless augmented by more air units from their naval reserve.
