I personally have stamina, and I never find myself running out of endurence, as long as the fight is not longer then about 5 minutes, having said that, that's constantly using endurence heavy powers.
Without it, I think I could last about a good two minutes before it runs out.
It isn't really required, but it is a convinience.
Seen some post about the Stamina power around on the forums, but I can't realy find a clear answer for this:
Is Stamina worth it for a AR/Traps build, or doesn't AR use as much endu as other powers?