Did you die yet?

That'd be rough without fire resist on the armor. Props for trying!

Good job on your solo attempt. Maybe next time you'll do it.

As for your handgun of choice, that depends on what you want to make out of it. Polaris has a standard clip of three, and the splash damage makes it easy to hit him, even with the shields up. It also has the benefit of shock, which deals additional damage (not really a whole lot though) and also interrupts his movements, making him easier to dodge and overall easier to deal with.
Argent Peacemaker on the other hand is purely offence-based, has twice the clip, and fast bullets. It does outdamage the Polaris, but you don't get the supportive shock.

So, unless you're aiming to kill him as fast as possible (which means Blitz Needle would be ideal, but save that for when you're experienced enough to handle it), I'd say go for the Polaris. It's a bit slower than Argent Peacemaker, but it's safer to use.

I recorded a no-death solo with my Polaris and it took about 35 minutes. I believe at full heat it does 108 on the expanded shots.

Best way IMO is to use Blitz, but you have to kill slags first, rest is not very hard. You can watch Exileddread and Viet's videos how they killed slags.

With that gear I'm very impressed that you made it to phase 4. Sure you don't NEED great defense and fire resists and high dps, but things tend to be a bit easier when you can afford a few screwups. So props for that.

The Blitz is great if you have one with mega CTR and ASI. The one I have now is ASI low, and I have a hard time making a go of it in my full gunner gear which bumps my CTR up to VH and my ASI up to high. I'm not gonna try a Blitz-related solo until I have a constant 4 bars at least.

What do people think about CTR-augmented charge attacks from a Voltech or Prismatech?

indeed, the fireballs stop a lot of shots, especially in phase 5.

How about a Cryotech? charge-freeze, kill some slags. Charge-freeze, water a fireball. Charge-freeze, another fireball. Wait until he's naked and alone and stab the heck out of him while dancing around him in a circle. I think I'm gonna try this technique sometime soon.

I didn't time out the different phases, but you can feel free to pick apart the video. http://www.youtube.com/watch?v=jkIRLbvHCrw

Also, if you're dousing the water balls in phase 5 to jab him in the knees, concentrate on the inner ones rather than the outer ones. The outer ones orbit far enough to skate around you harmlessly when you're right up against him. While it's a risky tactic, with a bit of careful running between the four fountains (never go back to the same fountain twice in a row, they take too long to respawn water drops) and good timing to hit 2-3 fire orbs at once, you can extinguish the entire belt solo without freezing.

It took me forever to solo Vanaduke on my own. Though I was trying to do it essentially blind (with my first guild, we never made it past the first level because I was the only one in 5* armor, everyone else was in 4* if that.) But your loadout seems pretty solid for what you're trying to do, the only thing that I had that you don't was a Shivermist and Skolver instead of Ash Tail. If push comes to shove, try upgrading your Gigawatt Pulsar to Polaris or one of your Ash Tail pieces to a Vog Cub piece. In either case, the Shock status from Polaris/Gigawatt should help keep him immobilized long enough to dodge things coming your way.

From what I can see it definitely looks doable with the gear you have though, so if you haven't already done it, good luck!

Also as Nicoya says, focus on trying to douse the inner ring if you're going to stay close to him. Even if you only douse two of the four flames, you're going to be moving a lot in that ring anyway so just follow the direction the inner ring is spinning. After that it's just knowing when to back off to avoid damage. :)

Well all I can add is how not to do Vana. http://youtu.be/G8vtCOGnIws
Other than that learn how to dodge and avoid taking damage.