Since the online WWS -> TPS converter seems to have gone MIA, I've put together a quick offline script to calculate the same information.
It's attached to this post. Caveats:
(1) It's a quick hack. Consider it a reference implementation that can be improved upon.

Seriously, though, any programmer with more time than I should be able to take the basic logic and go from there pretty easily.
(2) It's run from the command line and doesn't have a pretty GUI interface (I'm using a Mac, and any GUI I wrote would be useless for most people, anyway). Supply the URL of a tank's WWS page as the argument, or provide the contents of that webpage in a file and supply the file name. Alternatively, feeding the webpage to standard input works also.
(3) It's written in Ruby and requires that Ruby is installed on your computer. That said, Ruby comes pre-installed on Macs and most UNIXes.
(4) I've done some testing to see that the numbers look right, but there are no guarantees. In particular, I'm pretty sure that I missed a few non-standard abilities that generate threat (such as a tank using Stratholme Holy Water on undead bosses), and I'm not sure that I've accounted for all paladin abilities (all common seals should be supported, though).