I've always thought reap should be 1 HP per man in the unit. So early game reap gives you 3 hp, if nearly everyone is up, and late game it can give you up to 6. Seems like it would make it more useful and keep it more in line with how the + damage abilities work.

a percentage of max health would also work (for example, 5-10% of the unit's health per attack)

Just like everything else.

Always disliked reap, never made much sense to me and was one of those traits that seemed just to exist to force me too waste 3 levels  to get something else much better.

It's also silly to get +6 HP when you dealt 1 damage - which was all the enemy had left = P

Even sillier to get 6 for 1 when you're too weak to do more than 1!

@nighthavvk  Yes, reap, as it is currently implemented (+1 per unit on successful melee hit) in the early game, when +1 is a significant percentage of a troops health, is worthwhile.  By mid game, reaps utility drops when compared to other training choices.  Making it +1 per figure (as suggested above) is one option to keep reap more competitive as the game advances. 

I just imagine the AI fighting another AI with this skill, and they both do 1 hit damage, healing 6hp every time.  Infinite loop.