The body is relevant though because it will clear a minion the next turn, thus effectively healing you further in the long term. After you recover 8 HP on turn 5, the Hunter likely won't be killing you Turn 6 unless you were AFK for the first 4 turns. Having a huge heal is more important vs a deck like Freeze Mage, but you aren't necessarily going to win that joust (high chance they pull an alex or something)
I should've been more clear on my curve point - I was preemptively explaining why this card being cheaper than healbot doesn't matter (not saying that's an issue you brought up)
The way I see this is
Healbot:
+ Always heals 8
+ Always leaves a 3/3 body which will likely effectively heal another ~3
+ Better in more matchups
Healing Wave
+ Can heal more versus one specific matchup (about 60% chance)
+ Is cheaper
- 40% chance it heals less than healbot and leaves no body
- Will usually just Heal 7 for a card against everyone else
(note: my joust percentages may be off. I was using the Mid Hunter stats from this chart
https://www.reddit.com/r/CompetitiveHS/comments/3fwffh/joust_odds/ since Midrange Hunter has a comparable mana curve to Midrange Shaman, presuming you're playing the version with flametongues, creepers, mana tide, etc)
I don't really see why you'd run this card over healbot tbh.