The Kat/ Zoe reveal week is imo, the best set of episodes the show has ever produced. It was one bomb going off after another, sensational, but rooted in realism and character-driven storytelling. One of the reasons why I'm pro-SOC, laying realistic foundations will allow for high-quality drama like this to happen once again, as opposed to pulling big moments out of a hat and slapping them onto any random character.
Zoe finding out that Kat was her mum was actually completely downplayed, as it should have been. Instead, it was an exploration of how Kat became Kat, the stigma she has as a result of her abuse and how she is let down again and again by her family because of it. Throw in Charlie's angst of discovering that his brother is a paedophile and that his late wife knew about it, on top of the guilt... it was just amazing television. The moment where Kat sits alone on the swing and haphazardly applies her lipstick like a 13 year old would, before bawling is one of EE's most poignant and intelligent moments I think.
The Shirley/ Mick storyline was awful, totally unnecessary and it seemed like it was only conceived so they could have a "he's your brother" moment at christmas, a moment which wound up being totally forgettable because of how hammy the whole situation was. That storyline and Dean were cancerous to the Carters, who, up to that point had been pretty likeable.