LS,
I realize that Ork Hulks are more weaponized and militarized than the average floating hunk of rock
Understatement

The Orks manage to maintain 4 lances on the thing. Twice as much and 50% further reaching than those found on the Slamblasta, a singular miracle of Orkish maitenance.
Well if you look at the original model, a Ork Hulk will usually comprise of many many ships of all sizes. I think if you were to throw together 5-6 cruisers and 1-3 BB's along with escorts and such, 4 Lances is reasonable. The Slambasta is just ONE ship.
Turret value of 6. You are telling me that on that massive thing, with so much bare rock and derelict vessels, the race that is notorious for forgetting to set out adequate turret defence has managed to muster a turret density of 6?
"so much bare rock" <-- depends on the model your looking at

In all seriousness though, I feel they have the correct amount of turrets. This race prizes Hulks above EVERYTHING else IMO and they probably throw so many gunz and other crap onto it that it's probably not easy to attack at all.
Shield value of 3. This thing manages to maintain a higher shield strength than Orks can fit on their battleships across the entirety of the vessel?
Um... yeah! See above argument on how many ships a Hulk may have inside of it.....
Just remember, this is MORE than THREE times the size of a BB! It HAS to be that good. Otherwise, who would spend the $$ and points to use it?
-Zhukov