16 Communing and 9 Spawning is pretty good in general.
It is balancing out maximum effect and the amount of attribute points. Different spirits have this optimum point at different attribute levels, so check out the chart and make it work for you.
when i'm spamming with ritual lord, I prefer to get 16 in spawning, since it makes the recharge for the spirits so fast, it doesnt matter if they die a little faster...
If you are only using communing and spawning power, then I would say max spawning (12 + 3 + 1points) and 12 (+ runes) in communing.
In some PVE areas you may like to run 2 superior runes, as you may not be taking a lot of damage yourself.
If you are using other skills from a different attribute, you are going to have to work out where to cut back according to how you play.