Deus Ex: Human Revolution - Review @ HardwareHeaven
85/100 is the score for The Missing Link at HardwareHeaven, despite saying the DLC feels like a "deleted scene":
In short, The Missing Link spends a great deal of time going over the same game area and reinforcing the conspiracy theory plot. Having said that The Missing Link is tense and exciting with a lot to like and interestingly notable aspect is the boss fight. It gel's much better into the plot and setup than any of those found in the main game and allows the player to take down the final big bad in a variety of ways that best suit the players style.
Source: Blues News
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