for any orders to Qatar Thomann charge 40 euros, so if you make a large order it is well worth it. If you keep the cost of the order below 3000qar then there is no import duty at all.
I only once had to pay duty (200qar) on an order which was over 6500qar. I ordered a shed load of stuff for my band.
DHL normally deliver the item directly to your address, if however customs are unsure what it is, it will end up at Q-post. Been there a few times. The best time to go is 3:30pm it is dead in there around that time..