White. Not even a question. I see Purple, Silver, Gold, Green, and Blue all the time in T2, Teal makes it in sometimes, and even Red gets in on the action in decks I've played against. I mean, Clay was just released and I've seen more of that played than White in the past year. So...yeah, White. When your best card is used better by a more powerful brigade (TGT), you just get ignored (heh...).
For defense...I'm not even sure. Honestly, there are great T2 themes in every brigade, and I've seen them all. For least used, I'd probably go with Brown. Samaria decks don't work very well in T2 (since you can only have 4 Samarias), and evil kings for some reason just aren't as popular. Also one of their best enhancements is kind of a liability in a T2 deck when it is suddenly ripped and you also lose a good card for future games (you also cannot rip more than 3 and have a legal T2 deck, and even 1-2 can make them illegal if you're playing less than the max cards-per-soul).
