Dude, you probably don't quite understand what "double damage" means... ;) The problem is that the game tooltip doesn't explain this term, and many people misunderstand it.
The thing is, when Luck triggers, it doesn't double the final damage; instead, it only adds the base damage to the total (i.e., the base damage is doubled). And the base damage usually makes up only a small part of the overall damage.
This is just a common misconception. Let me give an example: a Death Knight controlled by a hero with 40 Attack points attacks some Centaur. Suppose the Death Knight has the "Double Damage" ability trigger, as well as luck in the same round. Calculating the final damage he will inflict on the Centaur looks something like this:
20 HP (base damage, which can range from 15-30 HP) + 55 HP (the difference between the Death Knight's attack and the Centaur's defense) + 20 HP (adding base damage due to the Death Knight's ability) + 20 HP (Luck also added base damage) = 115 HP. Of these, luck and the ability contributed only 17% each. So where is the quadrupling of damage?
And if morale triggers, you can deal another 20 HP (base) + 55 HP (the difference between the Death Knight's attack and the Centaur's defense) = 75 HP, which is much more effective than luck, which only brought 20 HP. That is, when morale occurs, on average, you can deal about the same amount of damage again. (I say "on average" because sometimes it's less, and sometimes it's more). In the case of luck triggering, only its part is added...
This is why I think that sometimes it's worth listening to other players instead of making unsubstantiated claims... Reiter was right.
Where did you get those formulas from? Trust me, in my case (by the way, in that battle, the casualties from the knights' attacks were my troops), the knights wouldn't have been able to take down those victims with a single hit. Believe me, even at a glance, it was clear that they simply couldn't.
Your formula may be correct; I won't argue since I haven't encountered this myself, but they wouldn't have taken them down...
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But overall, it's still good to have both. Well, maybe some people disagree, but that's just my taste. I love when my hero is an expert in all magics and wisdom and also has morale and luck.
It's a pity that such heroes are very vulnerable. I mean, there are artifacts that reduce the enemy hero's morale or luck, and then these abilities become just a waste of skill slots.