Yeah those are really annoying to deal with as a vanguard with a halberd. Not impossible though. The best players I fought against were vanguards with pole arms, and they chewed through everything like tissue paper.
On vanguards with other pole arms, it's a fair fight. There's really nothing to offer except don't get hit
.
The way to deal with Dodgy MaA is, if I recall their tactics correctly, is to fight conservatively to our stamina them, or alternatively just flat out outmaneuver them. It can be done. God knows how they do it, but a vanguard is still nimble enough to dodge and maintain his distance like a champ if he knows what he's doing. MaA just does not have the stamina to keep up with a vanguard while parrying his attacks. If I remember correctly, he did it through a lot of hit and run. Attacking at an extreme range of his weapon, turning 180 degrees and sprinting out of the reach of the MaA'a weapons, turning 180 degrees again while overhead slashing, etc.