Be sure you cut away every bit of soft tissue. If you save partial pads, cut into healthy tissue to be sure you've cut away all mush. Bacteria grow rapidly in the damaged tissue and can sometimes spread to healthy tissue when a plant is stressed or dormant, so be sure to get rid of that stuff. Opuntia species are fantastically resilient and easy to propagate. I have seen Opuntia pads root from between blotter papers in a plant press left over the holidays in a cold, dark botany lab. You needn't keep them damp. They have adequate moisture in the pads to feed new root growth, and they can't absorb moisture through the "skin" anyway, so my feeling is that adding moisture will only increase the danger of rot. Personally, I think it will root just fine if you lay it on top of dry soil. Just be sure the damaged portion scars before you let it get at all damp. Some Opuntia species are very cold tolerant. Others aren't. There is one species that grows wild around Boulder Colorado- Opuntia compacta maybe. That isn't your species, but it's easy to see why you thought it might survive such intense cold. I hope you can salvage some. It looks like one of the more attractive Opuntia.

From the pictures, doesn't look like anything is really wrong. Old leaves are supposed to droop and die, then new ones replace them. The Pleiospilos with the flower bud is blooming out of season so it's all mixed up, plus it needs full sun to get the blooms to open, plus it likely is in root shock from the repotting so no surprise it isn't performing at its best. You really should put each plant into its own pot, they don't all share the same growing needs so you can't really take care of them properly that way. Second thing is try to ID what you have and learn about their growth needs. Reading and learning is the key. Don't be discouraged by the inevitable early failures. Read more about appropriate soil mixes, pots, sun and temperatures. If you have the ability to grow these outdoors they will be much healthier than indoors. Succulents are not good houseplants. They are good at tolerating poor conditions but that doesn't necessarily make them for a windowsill. x

Your problem sounds more complicated than what you describe. More information and adding some pictures would help those reading this visualize the situation. Have you been watering the tree up until you worked on the mulch problem? Working on a stressed tree where you might have broken surface roots with the rake could explain the wilting. How much top soil did you add to the surface of the mound? It would take more than a couple inches of dirt to smother roots imo. How deep is the mulch? You only need 2-3" on top, to protect the soil from the hot sun and hold moisture. I personally would be hesitant using freshly ground mulch, unless I knew it was completely dead wood and bark. Heaping stuff on that contains green or sap wood, could result in various gases given off as it breaks down, at least for the first week or two. Did you water it good after you were finished? And continue to water as needed afterwards? If it's been really hot and dry there as you describe, anything that upsets the tree could cause it to react and show signs of stress.

I had similar accident few yrs back. Few succs got sprayed - they were quite 'spotted', but didn't die. I do not have Aloe vera. It took a while for all the leaves to get replaced by new ones...spots didn't disappear. I guess it all depends on what the sprays was (ingredients), and plants sensitivity. Your aloe looks quite red, maybe you should keep it in dappled shade for a while. Many plants could be more photosensitive if sprayed as Kara suggested. It is suggested to keep them out of sunlight while using any spray treatment - same would apply here...