Please note: do not criticise this post by talking about healing effects are blocked by inferno tower, just because of this it does not mean a troop/spell should not be upgraded, taking this logic in to account then why should be have level 7 barch with town hall 10s defences.
Now we have that out of the way, let's talk about a level 7 healing spell, the healing spell is good at level 6 but it is not too flexible when working with multi infernos, I usually find myself bringing 2 freeze spells when using my barch army against other town hall 10s, giving the healing spell another level will allow it to be more sufficient at healing troops and will make a nice addition to any army, here is my hypothesis on what I think the stats will be:
Healing spell level 7:
Total healing: 1800
Healing per Pulse: 45
cost: 26,000 elixir
Upgrade cost: 6,800,000 elixir
Upgrade time: 9 days
Laboratory required: level 8
