Well, actually they do, they use a gun like the Tenno do. So Adding Crit will make him do criticals. But this is nonsense at Sentinels
@KyteM How do you know this for sure?
The datamined stuff.
https://docs.google.com/spreadsheet/ccc?key=0Au6mBXle3cFtdHBYUzVJaDJfdkIzSEN1cUh5UlRvckE#gid=4
Sentinel weapons are included with the regular weapons.
Sentinel guns have 0 crit, since critmods scale off the base crit of the weapon, it stays at 0 no matter what rank of bonus critchance you put on it.