Heroes 5.5 WarGame Edition - Tactical Edition.

The question is, how was the plague tent buffed?

The tent, like some other things, such as ranged towers, was indirectly buffed by reducing the amount of "meat" in the army (a large number of active armies, faster game times). 100 hit points is a minus half a dragon, a huge benefit in terms of WGE, where dragons don't accumulate in armies in large numbers. I anticipated in advance that reducing the "meat" in the army would only benefit the game in many aspects.

Comparison with a ballista.
Damage (2-4)x, attack 15, initiative 9. Average damage at the start is (2-4)*5 = 10-20 (due to the higher average starting attack and knowledge stats = 5). In the middle of the game, the damage will be about 30-60 per shot, with a triple shot of 90-180. The tent's damage is formally lower, but it ignores the target's defense + has higher initiative (10 versus 9), so in this case, the tent is approximately equal. The downside of the tent is the limited number of shots (it makes 4 instead of 3), as well as twice the lower survivability (defense 5 versus 15).

As for the comparison of the plague tent's shot and healing, dealing damage works much more effectively than healing (with the exception of reducing losses in breaking through). At least because for the first 1-2 turns, the tent can act while there is no one to heal; and also, the choice of target for dealing damage is many times greater than for healing (only the wounded).

Added 22 minutes ago

A huge amount of work has been done - even drawing the diagrams took a lot of time, not just the development itself - respect and kudos:smile20:

All of this has already been implemented in the game; essentially, what remains is:
1) connect the heroes, set up the starting troops and spells
2) connect the artifacts
3) set up the banks and map generation from GSC (guards)
4) another unit rebalance
5) scripts (implementation of working skills and perks)

Compared to what has already been done (units, spells, classes, the wheel, prices, city layouts), this is not much.