Bugged: They have allies, but so do we

I have seen the problem coming up in the forum but did not find a definitive solution for the problem. The last quest in the Worgen story line:"They have allies, but so do we. is impossible to finish, they shuriken thrower can make short work of orks and wolf riders, but the ork war machines flip out when you shoot them. They evade, are pushed back, sink through the ground or just plain disappear. I can do about 200 damage and then they reset, usually at a different location with full health.

This is the last quest (I believe) for the Worgen to leave their starting zone and I would like to finish it and head out in the real world.

Is there a solution to the problem or is there an alternative to get out? Much obliged.

Edit: I think I can do this... one way is to drive all the way around the orks and shoot one glaive at a machine, wait for it to charge you and then shoot it, one glaive at a time DOWNHILL. if it goes uphill it will fall through the ground. Just shoot it one, wait for it to bounce and repeat, chase after him.
They can bug out and leave combat, they will evade everything then, repeat as before. Be carefull that downhill usually means through alllll the orks...

I just settled for clubbing the snot out of one. Save mana for heals and wear it down in a safe place. Great.