At 63, 56 on the map you have 3-4 fenrunners to kill, and just west there are 2-3 fenrunner just outside of the camp. It took me 25 minutes( i was also killing crocolisk and mongril between spawns.) the fenrunners will take off at 10% but for anyone with any kind of ranged attack that's easily taken care of.

Such an easy quest... Simply walk near the water where there is no crocolisks... Did this quest so fast.

There are a lot around 20, 30

i found one at 31:35 in a deep pool hes near the middle of it under the water,
i have also found one at 29:28 i also found a Fen lord ( only a lvl25 )

If you want to find those mobs, here's a few tips that might help you.

-The mobs are invisible, therefor you might have to enter the water before you can spot them.
-You want to look in the riverends, not where the stream of water is thin.
- You want to look in the small ponds.

That's how I did, and that's where I found all 8 of them.
If your smar you might want to ask a warlock to buff you with detect invisibilty. If it works or not I can not say, but it makes sence that it would.
Also, if you travell further west you might end up with Fen Lords on your back. Those are level 26 and can hurt pretty badly for somebody who isn't prepared for it. They seem to make alot more damage than the creepers.

Also I must point out that blizzard has to love being cruel, why oh why did they have to make the water so deep you can't just run but you have to swim?

Hope it helps.

In the Wetlands there are rivers and ponds. You can find Fen Creepers in almost every pond. So follow the rivers from pond to pond and you'll do ok.

Takes under 15 minutes that way.

I'm in the process of doing this quest, probably for about the tenth time (with the tenth character) and I think I've found the method that works the best.

Get an engineer to come along and wear a set of Catseye Ultra Goggles. It works better than track stealth, and you MAY actually find them far enough in advance that you can get a charge in on them before they attack you.

Yet another use for engineering. :-)

Piece of cake, as druid just walked along the river from 46.27 to 48.37 in cat form and got the lot in about 10mins

I found this very easy as a Lvl 25 Gnome Rogue...
Just follow the small strands of creek from the Warden guy down to Sundown Marsh.
Although just be aware that you also may aggro a level 21+ Crocolisk ..as they hang around
the water.You will probably see through there stealth when you are about 10 yards away from the
actual Fen Creeper..

Hope it helped ;))