senti is the same role as duelist: rely on mechs and take space. Only actual difference is that duelist util is meant for taking space, while senti util is placed down and meant to hold space, which is why the senti lurks. Senti is just by far the easiest to switch to from duelist.
They knew which setup best to counter enemy duelist since they knew duelist habit. However, there's some problem they need to handle as sentinel such as fighting enemy on their own (they used to entry/fight enemy with util support)