Rogue is a monster of an ally whose stats can often reach 4/4 every turn! You can always trigger her ability by targeting your identity, and in fact this should be preferred to targeting an ally (though Professor X or Nick Fury can afford to take an extra damage). Rogue is also hands down the best X-Men to carry a Protective Training, and in a deck with 3 Game Time she can go absolutely bananas. One of the most exciting cards from Nightcrawler for me and worth using many deck slots to optimize.

If you can sustain 1 damage per turn, which shouldn't be too much of an issue when playing Protection, Rogue can turn into an absolute goddess on the battlefield. Very few allies have instant access to 3-4 stats right off the bat. She has that! Most heroes easily have 2 THW/ATK, and getting hit by 1 damage for 2 extra stats on Rogue is definitely worth it. Grabbing Protective Training and Danger Room, and/or Med Teams provides a flexible 3-4 thwart or attack from her round after round, which is good enough to build around. One of the absolute best allies not just in Protection, but every other aspect!