To be honest, I hate Vital Strike. I think it sucks, but a buddy of mine wanted to make some 6th level brutes and duke it out so I thought I'd play devil's advocate and see what I could get Vital Strike to do at the earliest possible level. Here's what I came up with:
Any Race/alignment
Guide/Shapeshifter Ranger 6
STATS (15 pt buy) no racial mods included
STR 17+1 lvl+2 enlarge person = 20
DEX 12 -2 enlarge person = 10
CON 12
INT 10
WIS 12
CHA 7
Feats:
1.Exotic Weapon Proficiency: Bastard Sword (not sure if required, extra feat slot anyway)
2.Weapon Focus: Bastard Sword (bonus)
3.Power Attack
3.Endurance (bonus)
5.Furious Focus
6.Vital Strike (bonus)
The Guide Archetype nets us the awesome Ranger’s Focus ability 2/day to get +4 to hit and damage against one target (swift action to activate).
The Shapeshifter Archetype grants form of the Bear for +4 enhancement bonus to Strength usable for 7 rounds/day (swift action to activate). It also requires us to select the Natural Weapon Combat Style which gets us Weapon focus at 2 and Vital Strike at 6.
Wealth by level dictates 16,000 gp which we only need a fraction of--enough to even fit in the NPC wealth guidelines for a CR 6:
Large-sized Masterwork Bastard sword (-2 to attack rolls, 2d8 base damage, two-handed weapon) (335 gp)
Permanent Enlarge Person (2500 gp)
This increases the base damage of the bastard sword to 3d8
Lead Blades spell (memorized twice in this build) increases the damage of your melee weapons by one step for 1 min/lvl (4d8 for bastard sword)
Sequence:
Round one) Standard action: cast Lead blades, Swift Action: activate Form of the Bear, Move action: move toward target and draw bastard sword
Round two) Swift Action: activate Ranger’s Focus, Move Action: move next to target, Standard Action: Vital Strike activating Power Attack
The Math:
Attack Bonus: +6 BAB +7 strength +1 masterwork +4 Ranger’s Focus +1 Weapon Focus -1 size -2 oversized bastard sword = +16
Damage: +10 strength +4 ranger’s focus +6 power attack = 8d8+20 (average 56, max 84)
Average Fighter’s HP at level 6 assuming 14 Con and all favored class bonuses to HP: 55.5
Now, this build is far from optimal as it has many things unused (race, traits, magic items, potentially one feat slot, etc), but you get the gist. In general, Vital Strike is not that great. You're sacrificing lots of potential damage from multiple attacks, especially if you miss, and there are quite a few ways of negating one attack/round. If Vital Strike is ever good, it's at 6th level and this is a great example of how.
