it is possible to plant the banner without clearing the area first, but I don't recommend it. lvl 80 mage had 15k hp and 2050 AC, I sent a pet with Grounded Stance and Aegis to attack a spider once i got to the center. As soon as i appeared I right-clicked the banner and completed the task stage. I got hit several times and ran out of the circle of death with 9% health. ran circles in the little valley there (with lev) while on mount. clicked of mount for a fast stop and gated. I made it out alive but it was an intense run. Next time I'll bring a friend or two and clear it first =-)
One thing to point out to those equally as dimiwitted as myself: you must Use the banner as if it were a book/potion etc (right click from inventory). I was expecting to get a task update just for being at the correct location, as with similar tasks in TBS and TSS. Duh!