Voice comms is a huge advantage, and if as a group you are not using them and stomping people, think how much worse it is when premades do have that advantage. You cannot compare typed chat to voice comms.
QFT - It can't be said enough. If you don't know your teammates and IF this game had built in VOIP, imagine how much better it would be? I don't know JimmyBlueShoes the gunslinger. I don't know his play style, his skills, his strengths or weaknesses. HOWEVER, if he starts talking and I'm listening or vice versa, we've summed up a going part of it right there. NOT EVEN COUNTING the speed of voice over typing or the fact that we can keep fighting instead of typing.
If your team can PVP with no voice, great. If you've been playing together for a while and just "know" where your team is going to be, kudos. That's approx 0% of the PUGs out there.