Neither of which are needed. I rarely bother with blade barrier because I don't take maximize or empower. Without them, the spell is laughable. Even with them, it requires kiting enemies repeatedly through the blades.
Cometfall I do take, but heightened, quickened soundburst and greater command both work just as well at level 12, especially because I could care less about the damage that cometfall gives. It's all about the CC.
Of course, your mileage may vary. I'm talking specifically on reaper (low skulls and up). In reaper, heal as a spell greatly exceeds heal as a scroll. And I don't mind the heal SLA as long as the cooldown is not shared with the heal spell. In reaper at 12, I'm often needing to heal multiple targets that are not close by and I have very little access to mass cures at that point.
Regardless of whether you play a FVS to heal or not (my FVS build is not a healer), there are some must grab spells regardless of what your goal is. Heal is one. I don't think the Heal SLA would replace me grabbing Heal. First, I can't see my build taking T5 in this tree. Second, if I was going to go that route, then I want to maximize the number of healing options on different timers as possible. Thus, I'd still take the heal spell AND the heal SLA as level 12.