Personally I like the Sentinel in 2/3 the best but in 1 they don’t really have the specific niche purpose that they seem to in the sequels, since all dual classes just get half of the powers from each.
ME1 I just go full Engineer and select AR training.
It’s always AR training.
I like that the Sentinel ends up having a tool for every situation. It’s good at handling armor and shields in 2/3, and gets a good defense option in tech armor. It isn’t as flashy as other classes, but it’s great all around.