Vexcali is a dangerous support weapon almost unlimited over shield as long as you have ammo and balance your shooting and stabbing... I haven't used it in a while but it's a very nice cqc kill stick
Well so far the projectiles it fires is literally a projectile. So that's something to get used to. There's a cycle of guarding, blocking damage and working with the overshield to make it work but I haven't quite figured out the rhythm yet. I'm certain in PvE it works much better but I prefer PvP.
The overshield works like this: you guard, you get a very small bit of OS. When you down someone with this you get a full OS and if you keep chaining you can get infinite OS. The thing I'm trying to understand is when and where the extra damage is. That's what you get for having an OS with Vexcalibur. I thought that by pairing this glaive with Winter's Guile it would help but I'm not certain it's working.