Among the primary stats attack obviusly is close to be useless for healers since, at most, it gives a boost of chase damage.
But ok, that makes sense, is like for a full tai ninja whose ninjutsu usefulness is close to zero.
But imho some secondary stats should work differently for healers.
Lets take in account injury, critical and combo.
Yes all of these are claimed to have two effects: the active part and the passive part.
Now, since we know attack is close to be useless for healers we just don't give them the best attack magatamas, inner gates and so on, and this makes sense, but for the secondary stats i was talking about this could be not true, because healers greatly benefit by the passive effects those 3 grant, so you want to give them a good level of combo because you don't want an enemy standard attack starts a combo on them, you want to give them critical because you don't want an enemy ninja to crit on them and you want to give them injury because you want that when the enemy crits on them then lands the lowest possible damage and this is so because you want healers, like tanks, to survive the longest possible, while you want, instead, strikers to deliver the highest damage, so you give them these stats for the active part mostly and not for the passive one.
The point is that by adding those stats to strikers for the active effects they get also benefit from the passive effects, while healers, to whom you give them for the passive effect, don't get any advantage from the active effects.
Now, the suggestion is, for healers, to double the effect of the passive part since the active one can't be used at all or just give them a close to insignificant boost.