My first thought after watching the video was it's a bug too, maybe some copy paste bug from timber.
But thinking again - I thought 'no', this is not Exactly bug, this is a design error. Either design error, or Heroic timber is designed on purpose this way, to have high (1)base damage and (2)actually do small damage on hit - you see, they, (1) and (2) are different things - base dmg is also used for other things like in the formula of some computations of pet's AA.
Every pet's passive ability has a name.
You see on the picture of Samael up - bellow Pasive Ability: there is the phrase: "Infested touch".
These passive ability change with level, "Infested Touch" is the last passive ability of Sam.
You see, these different passive abilities are something like the char classes abilities (for instance firebal,ss,windmill,etc), but are designed especially for the pets, each has its own animation(more visible on passive abilities of ranged pets), and only pets can use these Abilities. And the final damage of these passive abilities is determined by the 'base damage' (pretty much like with char's abilities). Am I right, saying all this, devs?
If the 'base dmg' was the only thing that mattered for pet's actual dmg - then all pets from one type, for instance legendary, would do the same dmg, but they don't do same. And some attack one target, same many.
(Off-topic: I'll mention here also my 'pain', that in last expansion char's dmg doubled because of new weapons with dbl dmg, but pet's dms stayed almost the same because pets don't have weapons, and the importance of pets as a damage dealers with their passive was cut in half; which is a lot, nekro's passive really helped at 56; i think new formula for pet's passive should be valid after lvl56.)

Obviously, Heroic Timber (currently) has the same passive abilities as Timber - I can say this because at stable I can see that at lvl1 both have passive ability "Bite" at lvl1, and on final lvl Timber has passive ability "Savage Bite" and Heroic Timber has the same - can be seen on the picture in the announcement thread.
So if the devs do not change the Passive Abilities of Heroic Timber, they cannot make bigger the actual dmg of his passive - because now the herioc pet is stuck with the abilities of a rare pet, and even having far bigger Base Dmg cannot compensate that Passive Ability is weak, as ability.

In short - some new passive abilities has to be designed, for this "error" to be fixed, the heroic pet to make bigger actual dmg.
(And my personal suspicion is that they decided to let these pets so fast, that they didn't had the time to make pets with unique design, let alone unique passive abilities. This ofcourse is a suspicion, i maybe wrong and the pets are planned this way from a long time.)