I am super late to this thread, but I’m playing a ME1 imported renegade female infiltrator (the male voice acting is SO awful) and the bullet time kicks ass. Once you get a dozen squad points you can have over two seconds of bullet time every time you zoom in. On almost all lesser enemies one shot, one kill applies, especially if you get the headshot upgrade.
Vanguard is probably the shittiest (hardest) class to play since most enemies are either way more numerous than you, or outright stronger than you in melee.
And yeah, to anyone who hasn’t played it yet and is thinking of playing it, or is not very far in the game: do all the missions you want to do before taking the IFF mission. You will be committed past that step.