I agree with Helston, that shards should be gradually introduced into PVP events, since in-element placement has provided a general nerf to them -- although some are still OP (like SOSac). War is the largest scale event involving the most players and a fairly long period, so it would be to drastic to experiment with. So they should be tested first in tournaments and other shorter and smaller events.
Their general exclusion from all event is no longer justified. Some of them are definitely weaker than several plain bazaar-available cards.