Actually the mask stage wasnt such a big deal I got through it on the first try in under 10 minutes, My only major problem with the game was how they dont always inform you that you need to stock your deck with certain types of cards, like my first time fighting Metal gear too about 2 and a half hours because most of what I had were anti troop weapons like machine guns and a couple of cyber ninjas (which were the only things besides stingers that I could use to fight it).
Yeah sometimes you'll get a bad shuffle too, which will totally ruin your day but you tend to figure that out pretty quickly and assuming you saved before starting the level you can always go back and address that issue. That's the biggest problem with card battles of any sort, having the right cards.
I don't exactly consider the plot corny, it's just more confusing and filled with a lot of names to remember and more"scifi things" than I'm used to with the series, also much like the GBC game it seems to bypass the general timeline of the regular MGS games or atleast take place before the events in MGS2. The story would probably be easier to follow if it were voiced rather than all text.