Actually, no. It's good to know or at least try to guess who will you be fighting. For example why would I take a biotic when I'm going to shoot the geth (Team Headshot is almost perfect for this)? Or why would I bring a krogan against Eclipse, when I'd make a better use of an engineer and a biotic. And I would rather take a team biotic - sniper against the Collectors (or if I am a biotic, two snipers). Now I noticed that when you don't need an engineer, you need a sniper. Legion and Garrus are pure perfection. The Widow wins everything XD