While building a serpentine eidolon for a level 10 summoner I noticed what appears to be a rather powerful combination of a feat and a couple evolutions.
As it is written it appears that Vital Strike works with bite, grab, and constrict for some pretty obscene damage.
Before gear or anything else his damage with the single attack is initially 2d6+7 base(constrict 2d6+7). With Vital Strike it becomes 4d6+7 for the base attack and the wording for constrict is, "Whenever the eidolon successfully grapples a foe using the grab evolution, it deals damage equal to the amount of damage by the attack used by the grab evolution."
So it becomes 4d6+7(constrict 4d6+7), all as a standard action?
It gets more nuts when you factor in the feat improved natural weapon, and improved vital strike/greater vital strike. As a huge eidolon, skipping a lot of the extra buffs and whatnot, he would deal 3d6+11(constrict 3d6+11) but with greater vital strike he would deal 12d6+11(constrict 12d6+11)! As a standard action!
Unless I'm mistaken. :P
I haven't seen any official word on it, but i wouldn't allow the grab thing to proc the vital strike again.. but thats just me :0
And yes, Huge E's are going to do alot of damage. That is their schtick.
They continue to do alot of damage until confronted with a 5 or 10 ft door or corridor.. then they get the shaft. (potentially alot of them, if murder holes and spears are involved).
Being huge has to do good damage or it isn't worth the expenditure of points. being H U G E is just too big a detriment otherwise.
I also wouldn't allow the Vital Strike to proc again. The key wording is this:
...it deals additional damage equal to the amount of damage dealt by the attack used by the grab evolution
The attack used by the grab does 2d6+7. The Vital Strike does more damage not the attack. As an addendum, I wonder if the energy attacks evolution adds damage to constrict?