Wait a minute, wait a minute... Wizkids filed the suit, not WotC.
In a patent matter, who files first isn't important. Normally, the plaintiff is the one to file a lawsuit. In patent matters, either party can file. Filing first gives strategic advantage because you can pick a convenient venue. That means, if you think that jurisdiction X is best for your side, you file in jurisdiction X. Or if you think its cheap for you to hire lawyers to litigate in jurisdiction Y, and expensive for your opponent, you file there.
As for the "frivolous" patent, I have no idea whether its frivolous. Probably it isn't. The fact that wizkids went and made an (allegedly) infringing game while the patent was being processed doesn't make the patent frivolous. In fact, I don't know of any argument at all that supports the claim that the patent is frivolous, other than a general bleating about patents being evil, etc, etc, etc. I don't know that its NOT frivolous, but the fact that it got through the USPTO is a good prima facie case that is not refuted by merely insulting the USPTO and wotc's business practices.
And for the record, the patent office doesn't actualy grant every piece of crap that comes its way. A lot of those alleged patent abuses are either urban myths, or examples of people on the internet not being patent lawyers. Sometimes a company will seem to patent something that they didn't invent, but on closer examination, they patented an incredibly limited variant on that same something. They might go on to try to use that patent improperly to intimidate their competition, but that's not the same as the patent office improperly granting a patent.