More weapons would = a higher chance to win, and that's why losing the #1 weapon on offense (besides Brady of course) 2 years in a row during massive games hurt so badly.
I agree with your thoughts that we need to bring in another WR or two, but not any of those FA's who are going to cost a ton. It's too much of a gamble, and we have our own version of a top tiered, top priced WR who may not even stay, and he's averaging 100+ catches per year in 5 out of the past 6 seasons. It's the draft of bust...maybe a mid level FA signing if we're lucky. The WR corps isn't anywhere near as bad as many think, especially if we retain Welker.
The issue also lies on defense a lot too, more than most give credit to. Giving up 3 TD's in the last 1.5 quarters of a big playoff game is absolutely unacceptable, and unfortunately has grown to become the Pats usual standard in huge games. Giving up very long, entire field driving late game TD's in the past 2 SB's in the final minutes of the game BOTH times says a lot. It isn't about what the offense scored necessarily, as it is that we HAD leads in both of those games. That is the main point.
In Sunday's game the score was a 1 point game with 14 minutes left. The defense was the side of the ball that allowed that game to change. The offense just had an uncharacteristically poor performance that doesn't usually happen, and even then we're looking at 7/15 on 3rd downs, and 8 trips inside of FG range!!! About 90%+ of the NFL (if not more) would kill for that to be an "off" performance. The system here works. Maybe not when someone is knocked unconscious, maybe not when Welker drops another major 3rd down ball to open the 3rd quarter which should've put the game in a whole other dimension, and maybe not when it's blowing crosswinds at 25+ mph...but the system here does work.