[thejeff]

F9 get +4 attack and an armor negating attack
E9 gets +4 reinvig and +4 armor

The reinvig is nice with sacred mages, doesn't really help troops all that much.
The Earth protection bonus seems to help more with troops that already have a high protection. Helhirdings rely more on not being hit, with glamor and water bless for higher defense.

The higher your dominion the faster it will spread. Provinces with your dominion will adjust to your scales. I believe they will shift faster with a high dominion, but I don't know the formula.

You also can only buy 1 sacred unit per point of dominion.