My junipers have a lot of deadwood in them. I don't believe it is due to spider mites, as the spots began appearing after all the rain we had in the early summer. Can the junipers be revived? If not, can you recommend an alternative for a semi shady garden?
More information is needed here. Are any new shoots or branches suffering, or is the dieback only in old wood? Looking closely, are there holes about 1/4 inch diameter indicating borers? Are there cankers lower on the affected branches (darker or otherwise discolored, sunken, or weeping areas)? Are you brave enough to scrape away a bit of soil at the "flare" where the trunk emerges -- if so, is there discoloration or a bad smell or other abnormal appearance?
If there isn't any root rot they can probably be saved by pruning out the "dead" areas. Then practice good housekeeping by removing old and possibly diseased "stuff" around the plant and manage water as best you can. Can you open up the tree canopy to get them more light?