I'm happy to let you watch me on my bounty hunter to see just how wrong you are. When I say death from above has a delay, im not talking about the 1 second it takes to fly up in the air, im talking about the times where it pauses... does nothing for about 2 seconds, then your character rockets into the air and shoots, and many times if you take damage during that time, the attack doesnt happen at all. (Edit: and when I say it doesnt happen at all, i mean you do no damage but the timer reacts as if the attack happened.)
As for Unload, nope, wrong again... it does lose damage if you are taking damage... but I assumed it was working as intended since there are OTHER abilities on OTHER characters that ALSO lose time on the cast when attacked. I still assume its as intended, its not a cast bar, its a channel bar. Look at other games, when attacked while channeling the channel loses time also. Not an uncommon mechanic.