I don’t think so. As it is, a smart monster will smack the assault a few times, and as soon as the shield shows up, they walk away to do something else. Shield down? Finish the assault. Toggling it still grants the same amount of invulnerability but allows the monster to opportunity to juke out the assault by pretending to commit and making the assault waste their shield. Or giving the assault considerable survivability if they use the shield right. As it is, the assault is kind of like, “Walk in, shoot all the things, call it a day.”
Aside from the character abilities (Mines, Grenades, and Super Soldier), they’re all pretty simple. I think it might add a level of strategy to using the assault.