If I recall correctly, this is the one with two levels that make it confusing. once you enter the delve, the first big room is one of those with stairs on both sides. From there you can cross the room and take the top route to continue, but you can also take the bottom route from the lower part of that room. The skyshard (even if you have an addon or find a map) shows in the top corridor, but is in a sidebranch of the lower corridor. Cause this sidebranch is fully covered by the top corridor, it is hard to see.. So take the bottom route and look for a dead end side corridor there.