If all units were to compete Wimbledon-style...

[DGDobrev]

1. I am uncertain whether attack and defense play a part in the use of abilities. This is why I left it out. I will read through the russian guide carefully and I'll do some research. However, if it does play a part, the wasp swarm damage will be:
(1/(1+(66-50)*0.0333))*((70*0.8 )+70)

2. That is quite right, but I think you miss that the crit modifier is 1.5, not 1.75, which puts the Ancient Ent's damage at the value I put in there (atk/def ratio is taken into account as you can see from the formula). I know that Jolly Roger from the gift bag improves crit damage by another 20%, but we're talking about pure stats here.
here's the formula I used:
=((1/(1+(66-50)*0.0333))*140)*1.5
everything's there - def/atk ratio, multiplier, etc.

3. That is a good point.

4. Wasp swarm is a ranged attack. Can you use in against an enemy that is right in front of the ent? I haven't seen the AI do it, so I surmise it is impossible (otherwise the AI should have used it because the AI always chooses the higher damage attack).
- waiting puts the AD at a disadvantage, because the Ancient ent will always retaliate to the AD's attack, while in the meantime he will take damage from wasp swarm, even if it's lower.