Agreed. At the point when the set was being made, they were trying to play it safe. Invulnerability is a very nice ability, and it helps to propel a game into later turns or break a close game in one's favor. However, that and Cosmic had potential to be too strong (if handled differently). I believe that, if they decided to revisit Team Superman in a later set, they'd become a powerful defensive combat team. A team-stamped PT called "Kryptonian Immunity" that negates a non-ongoing plot twist played while you control a Team Superman defender would be well suited to the affiliation.

Their deck manipulation powers are nice, too, but they don't make as much sense for TS as for some other team (I could see the League having had that theme), and it wasn't even all that good given the resources one needed to devote to it. The Daily Planet could've been a reusable version of Breaking Story, which would be nice, and had X-Ray Vision been done to manipulate their own draws, it would have been a nice means of letting Superman and his friends use their powers and resources to devise a better answer to a situation. Not quite up with Doom's or Batman's levels of raw control over their resources in-game, but pretty solid, all things considered.