League of Legends (LoL) Question: Lissandra build

Well, I've been looking at some of the Lissandra guides and I have to say I don't agree with those builds, or at-least a part of the builds.
What most suggest: RoA, Rabs, Liandrys.. etc
What I do: Haunting guise, needlessly large rod/Seeker's(vs ad caster mid)/Negatron cloak(vs annoying burst mages), chalice/morellonomnicon(If im doing well enough), Seekers(If I didn't need the armor earlier)/Negatron cloak(If I didn't need the mr earlier), Zonya's, Rabbadon's components/Rabbadons/Abyssal scepter, Rabbadons/abyssal scepter, If i need more health I'll sell guise to get a giants belt and then turn it in to Mogs or Rylais if not just finnish liandrys

Am I doing something wrong?

EDIT:
Generally If their team has an ap champion that doesn't do much later in the game I tend to go for voidstaff to replace abyssal
Tear is horrible on liss, but chalice is an okay item. Sometimes my blue is denied and I need a working mana regen engine. I usually just go for morello, though IF I'm behind, being denied my blue and don't have enough gold to get a morello then I get chalice.
Thanks for the answers, seems a lot of builds need to stop listing roa/athenes as core...