This is not true, the loss of life is denied by the other heal. However, the fact that your character's movement interrupts the casting (as far as I know) is not negated by another heal. So these things cannot be compared.
Ofc it can be compared, that's class design. Scout can shoot while running, Mage can not. Scout looses life, Mage doesn't. You can also compare it with a Warrior: Scout is ranged, Warrior is melee. Scout looses life, Warrior does not. Every class has advantages and disadvantages. If you remove the life cost of Blood Arrow, Scout looses its only penalty, which makes it... broken (in terms of class design, not talking about class balancing).
I don't want to remove the blood arrow mechanic but change it. I want it to be fairer, more logical and more enjoyable.
Me playing scout, blood arrow only triggers phoenix sometimes, that's the only thing that could be fixed, since it doesn't kill the player anyways.
I just want your gameplay as a scout to depend on you and your skills, not the heal and his skills.
Guess you are not dependant of a healer, you can also use potions to refill your life or use the buff more wisely. For the raid/group content, you always have a healer with you, so it doesn't even matter.
But enough of this topic for now, let's see what the Devs decide here I guess