That would actually be a significant buff to premade groups, since they would no longer need to deal with the problem of their heals getting "siphoned away" by other nearby non-grouped members of their own faction.Only ingroup healing goes against ESO playstyle and punishes hard purely casual players while merely annoys a bit premade groups.
Just for the record - a lot of players did state exactly that after the change was posted in the patchnotes.“We” thought that cross healing was too strong so we got healing nerfed by 20%. We thought to ourselves... too many people spamming rapid regen in a tiny area... 20% of 4x rapid regens is more than 20% of 1x rapid regens... this cuts group healing more than it cuts solo healing, this is obviously a good idea.
Oops. Getting melted. Solo players complaining they can’t heal. Surprise surprise, the 20 man group can still heal. Changed their gear. Not a big deal— they have protection. You can’t change your build the same way they did because you need to be balanced but they don’t.