I stopped at +18 on all of my heroes, because I prefer to use those 110 Emblems toward +5 on another hero than just getting the last two Nodes.
That gives me more overall depth and roster strength.
Those last Nodes are more useful on some Classes than others, and some people care about Mana Troops and shaving off a tile more than I do.
I’ve focused on Crit Troops because they’re better for tile damage, and more versatile overall, as they don’t require being a specific level before being effective. So the Mana boost isn’t particularly relevant for me, though it’s of more use to players who care about that.