Also, fwiw, my friend has a 2wd i-beam F150 on a Skyjacker 6" drop bracket lift and I can attest to how hard this has been beaten and is still fine; it has ample support and bracing to the frame. I agree, it does create a larger lever for the suspension to twist against the frame, but not to a catastrophic degree. A 2" drop bracket with appropriate support is not going to make your suspension weaker. It has its benefits.
I agree completely. Skyjacker's Class II stuff is pretty darn good as far as bracket durability goes... Infact, their brackets are likely stronger than the OE brackets (their extra width and inner connection more than offsets the added leverage by redistributing lateral forces across a wider part of the frame).
But yeah, by far the biggest thing is the steering.
Just to clarify one thing in your last two posts, it still is very possible to have a mismatched arc that the steering travels through even with a swingset (aka crossover) setup if placement of the tierods is wrong... What's actually more important here (swingset or not) is that the steering (tierods) be mounted so that it's travel arc is
in phase with the movement of the beams
at ride height (usually this is simply a matter of having the steering be mounted on the same horizontal plane as the beam pivot axes). When things are in phase, tire wear (and handling) characteristics can be very good even with the stock steering link.
This is where so many lifts fail, and surely has contributed to the rap the suspension has. As I said above, numerous suspension lifts fail to drop the steering down the same amount the brackets drop the axle. This puts the linkage angle askew, which causes the toe to move out several degrees when you pile yourself, a few buddies, and everyone's gear into the truck (the opposite happens when you put tongue weight from a trailer on the back). This toe misalignment has a 10-20-fold greater impact on tires than the degree or two of camber change that may also occur. Many people don't realize this because the change in toe isn't readily apparent like the change in camber is, so people often put blame for their tire woes in the wrong place.
FWIW, packaging a swingset/crossover setup on a 4WD gets complicated because the front differential is right ********** in the middle of where the tierods want to be (forcing you to put bends in them for clearance). For this reason I run a K-Link setup on my rig (based off the "Superrunner" steering kit Superlift sells). A K-Link makes a rather small compromise in the geometry (affecting bumpsteer only at very extremes of travel) so that the tierods can be fully straight, maximizing their strength and rigidity. Like anything else, tierod (centerlink) placement is critical, but set up correctly (something Superlift actually failed to do on theirs), the setup works very well (as the 33,000 miles I got out of my last set of BFG KMs at the 50% wear point attests to), and is still many times better than the stock linkage.