There's no way that spine equals meleeing with 2 weapons. It's like using a sword/shield, but you lose all the benefits of that free hand...and the added melee defense does not equal the lack of offense - a lot of damage at high levels has nothing to do with if you spin/parry/etc. Try a bloodlusting guy with axe/flail/etc dual-wielding then a spear....I personally found the lack of offense a bigger problem than the spinning. Even two rounds of axe with faceslash/Slasher was better than Vault and 2 rounds of combat with a spear. The only real huge benefit of Vault is the huge bleeding if they make it out alive.

I didn't say it wasn't possible, I'm just saying there are better options. Waking with faceslash is plenty fine usually for landing the kill like vault, and can be done while they are awake for the same lag. Arials also have better vaults, so if you're vault happy you should them out.....I've done an arial spear AP and it was alright, but it just wasn't my style.

And until you understand the true power of crippling strikes (it's not -dexterity), you won't appreciate it enough.