Whilst talking with Snake and Aslan last night in the IRC chat room, I finally realized that the Klingon ships were definitely off-target, as far as my view of the ships goes. So, being me, I took it upon myself to tighten the designs up a bit for the Negh'var, B'rel/K'vort, D7/K'tinga and Vor'cha classes.
B'rel Class Modifications
The B'rel, for the most part, looks fine; however, the warp drive and cloaking device were not available when the class first launched.
For a pre-2310 B'rel, replace the Class 3 cloaking device with a class 2, and replace the STN6 warp drive with a STN5.
K'vort Class Modifications
I personally think the K-GDM-2 (x2) disruptors entry on the K'vort is a typo. Remove and replace them with 4 K-GDM-3 disruptors. This provides a penetration of 4/4/4/0/0 and a weapon reliability of B.
As with the B'rel, use a Class 2 cloaking device and STN5 warp drive for a pre-2310 K'vort.
D7 Class Modifications
I have to say that I'm a little confused by the 2150 reference for the D7's original launch date. That aside, the design looks mostly sound.
However, I'd recommend replacing the KP-2A (x1) torpedo with the KP-5 (x1, 2/2/2/2/0, B) for all D7s encountered after 2250.
K'tinga Class Modifications
The K'tinga seems to have fallen into the same trap as the K'vort, with K-GDM-2 (x2) disruptors. Replace the K-GDM-2s with K-GDM-4 (x4) disruptors. This provides a 4/4/4/0/0 penetration, with a weapon reliability of (C).
Vor'cha Class Modifications
The use of a 150-year-old disruptor design on the Vor'cha really makes no sense, especially since there are much more efficient weapons available to the Klingons in 2362.
Replace the K-GDM-3 (x8) with the K-GDM-4 (x6). This increases beam penetration to 6/6/6/0/0. Also, reduce structure to 40 and add an additional KP-6 torpedo. This increases torpedo penetration to 5/5/5/5/5, and overall weapon reliability to (D).
Negh'var Class Modifications
The way the Negh'var was built, it was a full 12 points under space. While I understand that you don't have to use the full space allotment for a vessel, there is a legitimate trend to do so for mid-to-late 24th Century ships.
The Negh'var also suffers from the 150-year-old disruptor issue, and it makes no sense for the most fearsome Klingon warship to short itself like that, when much more modern and efficient weapons are available.
Remove the K-GDM-3 (x10) and replace with the K-GDM-5 (x5). This improves beam penetration to 7/7/6/0/0. Add the KP-6 (x2) torpedo to the ship's arsenal, improving torpedo penetration to 7/7/7/7/7 and overall weapon reliability to (E).
Further, Snake found the Negh'var's shield threshold to be too low, and I nominally agree.
Increase the shield threshold rating to 17/4, and compensate by adding the prototype flaws sensors (-2 reliability) and life support (-2 reliability).
That should take care of most of the undergunned issues with Klingon designs.