Daverave, et al,
The following may have been written previously, if so I apologize for being redundant.
The springs (or airbags if there are no springs or even if used in combination with springs) are the primary suspension component and support the weight of the vehicle (not the shocks). They also determine the ride height above the axle (I am including any riser blocks and/or spacers in this).
Shocks are used in conjunction with springs and airbags. The purpose of shocks are to damp out the bounces. The shock valving affects how fast or slow the shock recovers from compression (how fast or slow it damps or responds to bouncing). Ideally you would like a critically damped set up that after a bump or bounce completely damps out in one bounce (rather than several successively smaller bounces)
The appropriate shock length and travel depends on the spring (or airbag) and the length and travel must be determined with the springs fully unloaded (extended) and if possible fully loaded (compressed) to the point the bump stops are contacted. Typically, however, the travel and length is calculated by measurement from the fully unloaded position to the bump stop because loading the springs to the point of full compression at the bump stop is not feasible.
In all events you do not want a shock to have less travel than the spring (or airbag) will allow if you go over a bump and the spring (or airbag) unloads. It can pull the shock apart. Similarly you do not want a shock to have less travel than the springs (or airbag) which would cause it to bottom out when it gets compressed going over a hard bump, as it will produce a hard jolt and it can damage the shock.
So getting to the spacers. If they are added or removed there needs to be an understanding of the shock length and travel range before making a change as it may cause you to need to replace the shocks.
Based on the discussion above it seems that the spacers were a bandaid to remedy shocks that were not the correct length. It seems to me appropriate (if you do not already have the measurements) to have the shock length and travel measurements made on your vehicle and make sure you have the appropriate shock length and range before deciding to remove (or keep) the spacers.
Relative to thee failed brackets. It seems like the mechanics argument for failure is similar to having the wrong size shock (not enough travel or length). The loads on that bracket in compression can be quite high but it seems to me that the loads in extension would be significantly less (the axle and suspension are a lot lighter than the truck with camper). This makes me wonder if the bracket design is insufficient to handle the loads produced by your vehicle/camper combination. The cracking is a sign of fatigue which suggests to me the bracket is bending and working that 90 degree bend. If that is true then it seems to me that the bracket is not stiff enough (too thin or perhaps not mounted appropriately or ?).
Spacers and other additions may not be addressing the root problem.
If you have not done so (apologies again if I missed this in previous discussion) it seems to me it would be appropriate to contact the manufacturer of the bracket and provide them with the weight of the truck (rear axle weight loaded) along with photos of the installation and failure (both sides) and get their opinion.
I hope this is of some help.
Edit:
This link might also be helpful
https://www.motortrend.com/how-to/1001mt-shock-absorbers-air-springs/