Kiting is NOT possible. If you get out of melee range of any giant, it will head to thurgadin, so pulling is not an option either.
Yup, the giants will head for the dwarves if not actively engaged for the most part.
You can charm mobs to prevent them from running to thurgadin, but there's only so many you can stop at one time.
The last wave (2nd wave to a degree too) is very MR. I doubt you'd be doing reliable charming. Even with OOS on the mobs trying to gate them can take 10+ resists.
If ANY giant reaches thurgadin, it will despawn the zone for 24 real hours, so bear this in mind before inconveniencing your server.
Thurg despawns for 2ish hours. If it lasts longer than 2-2.5 hours there is a bug and a GM should be contacted.