Don't sweat the quest. It's not difficult, just time consuming. I've done the quest from Freeport to Qeynos with 2 characters, and I'm getting ready to begin it with a 3rd tonight.
You'll need to kill 500 gnolls, as people have said. Not a problem at all. If you just take your time, and kill blue/green gnolls, you'll be XP-capped at 220% into 17 before you complete the quest. It's cool that way, because as soon as you finish the quest you'll ding 19 and get to start your archtype quest (You won't actually ding twice....when you ding 18 you'll be 99% in to 18 and have to kill one more xp-bearing mob).
The named mobs are just not an issue if you get a group of other people doing the betrayal quest as well.
The hardest run is through Nek. Get a higher level to group you (30 or higher, preferable) and most of the stuff in Nek will be grey to you, allowing you free passage (with the exception of some named mobs that I still have never seen).
TS is the *easiest* run you will make. If you take the shortest route between Nek and Antonica, there is absolutely no reason to die in TS. Off the dock as soon as you enter TS, run straight ahead and take the *first* right into a small canyon. Nothing in that canyon is aggro. Keep running until you get to the road (you'll see guard towers) and hang a right. Stay on the road, but on the left-hand side of the road to avoid any undead. The road leads you straight to Antonica and you shouldn't pass close enough to *anything* that is aggro.
The quest is fun and gives you a great sense of accomplishment. It's on an epic scale, without requiring a small army to complete.