Cass has problems. I have stated this more times than I feel like I should, considering how many posts there are and not one single red response, yet other champions get responses for a single thread about nothing. The main thread is here:
Support it if you care, Riot doesn't seem to.
As for skill order, I find I tend to omit W until 7-8 and focus on Q. Why? Q has a .9 ratio and is spamable to hell. Once you get good with it, you'll be golden and have people raging at you in mid. My style used to focus on getting TF as quickly as possible (Q at level 1, W at 4, TF rest), and spamming Q as harass. This works very well, but it's really about mind games aka luring them into a false sense of security and punishing them a higher ranked E spam. With this build, I get a Rod of Ages first and Boots of Swiftness because you are weaving in and out. I would also take Ghost or Flash with Ignite because I wouldn't need clarity early game because I'd have plenty of mana with level 1 Q.
Recently, however, I have found and nearly perfected my other build, and it is less forgiving but more rewarding because it focuses on Q and early game spell power. Q>E>Q>E>Q>R with MP Reds, Armor Yellows, and Flat AP Blues/Qs. No Mp5 Seals? Cass has a base of 16 armor and the yellows nearly double that, and she needs it. I get Clarity and Ignite, grab a Doran's Ring and hit mid. I start with 34 Spell power and my rank 1 Q does just shy of 100 damage over 3 seconds. Considering the cool down, you're looking at mega damage. Once you hit rank 3, you can easily drop someone from full HP to next to nothing with only a few casts. Depending on how things are going, I will usually have enough gold to grab a Blasting Wand on my first trip back. Why the wand and not boots or anything? If you're hitting with Q like you should be, you'll get a speed buff and since you're leveling that first, it'll be significant, but the amount of damage you're Q will be doing will be too much for most, if not all, champs can handle at this level. Next trip back, grab boots and then work on tear>Sorc>Rylai's>Abyssal>Thornmail>Archangels from there, I usually grab a second Abyssal. Why? It's a good chunk of MR and 70 AP.even if the passive doesn't stack, though Banshee's is rarely a bad option (It's free Kog Maw week, and I've found it's rarely up when you need it anyway). The downside to this build is I only have around 2200-2400 (with potions) HP, but I have over 400 AP and plenty of Armor/MR to make up for it. It's also pretty easy to get and I frequently find myself with a full build. If there is little to no physial damage on their team, feel free to replace the thornmail with Hourglass/Rabadons/BV or even another Abyssal Sceptor.
Anyway, more on topic to the thread:
I doubt she'll get buffs or bug fixes any time soon. While I haven't seen it myself, several have claimed that Riot says she's working as intended. However, I have yet to get a single response from Riot about Cass for several months, so I am as of yet in the dark.