The springs are more of a problem than the shocks. The front springs especially are very heavily stressed and you need a good quality hot rolled spring or a very very good cold rolled spring to get a spring capable of accepting the stresses without collapsing as you observe. The rear springs are easier to design to be capable of accepting the loads with a conventional cold rolled spring.
Even Lotus struggled with this on the Plus 2 with its heavier load on the front springs. For a while I used collapsed original Plus 2 springs on my Elan as they were cheap and gave the right ride height with a stiffer rate without further collapse
There used to be a local guy here who hot rolled springs to specification from top quality steel but he retired and no equivalent now. I buy front springs now from TTR but not totally happy with their life and my checks on their design say they are right on the limit of acceptable stresses
The various shocks sold by the normal suppliers seem suitable for the advertised duty if matched to a typical spring rate for that duty but I have only tried a few and personally have stuck with TTR in recent times.
cheers
Rohan