Well, lucky you - good old nutrient rich clay and some decent shade for shade lovers, lol! Your blue flowered bushes are probably Ceanothus (google to see pics) and don't give up on them yet - its the winter that's punished them severely, and they may yet show tiny signs of growth. If nothing by end of April, they're goners. Your cordylines too have been punished by the severe winter, so its not the soil's fault, or the shade's fault, or your fault... And if its any comfort, you're not alone, thousands of people have lost these two plants in particular, plus loads of others this winter. Check the Cordylines for signs of rot on the stems - if none, leave 'em alone and wait for new growth to appear up the stem or from the base - when it does, cut down to where it is.

Clay soil can be very hard work, I try to dig in as much home made compost each year and gradually its texture becomes less sticky, also some fine grit helps drainage.
I have found ferns in the shady areas grow quite well and there are many varieties.I have also planted a blackstemmed bamboo in a very dark corner and it has grown to over 6'and is sending up shoots everywhere!!! It does have it's 'head in the sun tho'. It seems to like wet feet and sun on its leaves.There are also some varieties of Clematis that don't mind shady sites as long as they can climb up into the light.
Or if the ground is really wet have you considered raised beds or maybe making a boggy area or pond?
Good luck with it all.