Deirdre being absent for so much of the recent drama was unavoidable as Swmc says. It's a time when we viewers need to accept that we need to suspend our disbelief.
I do think her absence could have been written better though. If, say, Deirdre had an accident whilst at Bev's and was laid up in hospital in traction, it would explain her absence but not be serious enough for the rest of the family to be constantly at her bedside. We could have got little comments like they were just back from visiting Deirdre etc, so it needn't have impacted on the storylines.