Hey there MonMon!
Ventrilo is not required - however, aside from the obvious social and communicative convenience of speech, Ventrilo is very effective in combat. In a situation where reaction time is key - Ventrilo is strongly encouraged.
We have a few members that do not have microphones, but they use Ventrilo to listen and type to communicate with us.
Hope that helps and we'll see you online in the retail version MonMon,
VV