Heroes 5.5 WarGame Edition - Tactical Edition.

Also noticed:
You can take both a tent and a rapid-fire weapon at the same time. Again, there's no alternative. According to my scheme, you'll have to choose.

How is that so? Are you sure you read the descriptions? There are plenty of alternatives.

Even if the Plague shows weak competition (with a tent charge of 6 and the fact that due to the small amount of meat, the relative power of the tent is 2-3 times higher than in the original).
There's also Military Craft (+3 initiative). The ballista will have a base initiative of 9 (for the enchanted ballista).

Accordingly, Military Craft gives +33% initiative to the ballista and +30% initiative to the tent. Against +50% damage to the ballista (triple shot instead of double).

There is also the Artillery branch. -10/20% loss of enemy units even before the battle. Or level 3 firearms (for WGE, ignoring 50% defense +50 damage on top, this is comparable to a triple shot in power).