In Terminal I would recommend being 2 players, because I found I rather hard to play it solo. When you are 2 players, one can attract the enemies attention meanwhile the other flank and shot them from the side, from where the Riot Shields can’t protect them. There are a lot of counters you can take cover behind, so use them.
In the video tutorial below, there is a good example of how to flank the Riot Shields.
Slinky's Blog 