Tiffen filters aren't good buys at any price. Spend the money for a quality filter whenever you want to put something in front of your lens..
Actually, Tiffen makes both low quality and higher-end filters. Same is true of Kenko and others (Kenko are likely made by Hoya, since they are the same company).
Same is true of Hoya and B+W... they both make a range of qualities from low-cost, uncoated, aluminum frame, entry-level to expensive, high end, "nano" multi-coated, brass framed filters.
Last time I looked, Hoya had the widest range of Circular polarizers... five or six different qualities across the spectrum of price ranges.
Cheap filters are almost always a bad deal... more likely to cause image problems.
In this case, the focus problem looks so bad that I suspect it's actually not a circular polarizer, but is a linear. Those often mess with autofocus and cause focus errors, which might be worse on some lenses than others. Linear polarizers also sometimes cause metering problems on modern cameras. Linear are cheaper... worked fine on most older, manual focus cameras and lenses... just aren't usable on modern AF systems.
A CPL continues to be one of the most useful of filters in the age of digital photography. Some of a polarizer's effects are impossible or nearly impossible to replicate in any software (most other filters are pretty easily done either with camera settings or in post-processing). CPL have a number of uses, so I HIGHLY recommend you get the best quality you can.
I mostly use B+W Kaesemann. Hoya HD3 and EVO are very good, too. I hear great things about Marumi, as well... though I haven't yet used them personally. Singh-Ray and Heliopan are excellent, too... though they can be rather pricey.
