Just looking at the pictures of the ships, Sig, what do you find faulty about the statement 'The way those ships are laid out, they look less thick, but also look like they would be really good at turning'?
I believe its a matter of design philosophy over available technology. I don't believe the Imperials, based on their brute tactics, would ever dare to alter their hulls to produce a more elegant and efficient layout if it meant less bulky vessels. That isn't the same as not having the technology to theoretically do so.
That said, I actually like the idea that the humans, with their stagnant dark age technology, have advantages that few races can match, despite their horrible misuse of what they have. I'd be happy if Tau never figured out how to shoot at 60cm and the like, give those know-it-all blue boys something to fume about

Thats why I don't expect the fleet to play like the army, just as many BFG races function very differently in space.
I just know how Tau would want to operate, and I see their ability to making it happen.
@Horizon, using the Lunar was a bad example, will stick to chaos. Chaos have better individual ships, imperials win with team work.
My math doesn't support the Protector statistically winning, but 25cm speed would at least mean the Carnage didn't always have the initiative.
And I have through the math come to believe it is a bit better than I initially thought, but rather than a 170 point ship, a 175 or 180 point ship.
Just a smidge pricey.
Things so far we are agreed on:
Custodian needs 4th shield or prow deflector (I've come to like the prow deflector idea better myself.)
Cruiser status or 90* turns (As much as I think it would be a missed oppurtunity, cruiser status is certainly better than current.)
Tracking system increase to 20cm on Custodian.
Viorla variant negatives a tad harsh.
Speed buff on one or two vessels.
Think thats it right now.