The card I am referring to is Arcturus Mengsk's Stage II Command Card called "Tactical Mastery". It pretty much allows him to place down 2 additional command point regions.

This card is a brutal card in that it can quickly turn the game in his favor. That being said, I don't think it is unbeatable. The trick is put enough pressure on him that playing this card would end up being a liability. In a normal game where each player has two planets, it is not too dificult to set yourself up in such position.

My concern comes in with non-standard games. For example, if you decide to play a game where each player has more then two planets, it becomes more difficult to put constant pressure on your opponents. Once a player deploys the Tactical Mastery on a well defended planet, the game tends to go down hill fast. Last time this card came out, it took myself and another player to team up against the Arcturus Mengsk player to stop it. Does anyone else think this card would become a problem outside the context of standard games? If not, what are your recommendations to stopping it?

I haven't played many non-standard games; the way I usually play is we take 3 planet tokens and choose two (to keep proportion).

In any case VP give ressource tokens, that card becomes no big threat (even though it's awesome!) It seems like Mengsk is a very defensive faction: hold two planets, add VP, starting w/ goliath and meidcs... That can be a party breaker and considering how Norad II (alias Duke) is not a great hero, Tactical Mastery becomes a classic choice.

The best solution I can consider is to see him comming and harass his planets so that he picks the hero card. Don't leave Mengsk alone too long , or else you'll have to team two to one against guard-tokened ares with goliaths ( w/ charon boosters) medics and defensive modules... and who knows what else...

Non-standard games? Just don't play with Normal and Special Victory. In such games you should use Galaxy Conquest or Survival (BW) mode.

If you want to play short non-standard games, allow players to gain CP from areas and don't remove cards "The End Draws Near" from Event Deck (modify game modes mentioned above).

There are no particularly effective strategies against Mengsk. Many factions should be treated in the same way: don't let your oppotents to fell safe on their planets. It's general, but mostly universal rule. Destroy their units, bases, block their resource cards and steal CP areas. As fast as you can... and as well as others let you do that. Or, if you can't endanger them, ensure that others will do it instead you ^^ .

The biggest weakness of this card it that Mengsk need units on areas to exploit additional CP. What's more, they may be used against him, if many players decide to invade his planets. Notice that Mengsk have no Leadership Cards supporting his economy (except possibility to use 2 Special Build Orders per round - Star Order), so lack of units will be final nail to his coffin.

BTW: Don't underestimate Norad II. Perhaps it's not a deadly hero, but hard to eliminate, what may be even more important for Mengsk.