If you only do 1 quest chain in northrend...

[Svpernova09]

Do Wrathgate / Battle For Undercity quest change, one of the best chains in the game and sadly it's going away in cataclysm. Currently in beta the quest chain stops at the cinematic, you never get to go to Undercity.

Source: http://blue.mmo-champion.com/t/26399150318/wrathgate/

Wrathgate/Battle for Undercity gone in Cataclysm
It's not bugged. The quest ends at the cinematic now.

[Oatboat]

I agree, you feel pretty epic doing this quest.

About the same caliber as the Deathknight quest to leave the starting zone. The big raid on Easter Plaguelands.

[Lyonheart]

they are doing a lot of that stuff in beta.. ive seen a few ( some broke still )

[Zub]

The wrathgate is really the obvious choice, but i'd say the Murloc king quest line (in borean tundra) is pretty epic too (in a different way lol) :-)

[Whowantstoknow]

Maybe its just me but I found the battle for Undercity extremely tedious. I will not be upset at all if they stop the chain at the cinematic.

[Nighthawk38]

/agree. The Wrathgate quest chain and the cinemtaic were all-time EPIC. I remember the first time I saw it, I just sat frozen at my pc, watching the monitor. The Undercity however was a real letdown for me. Stopping the quest chain at the cinematic is a great idea as far as i'm concerned.

[Slats]

I imagine they are doing this for technical reasons though.

Since undercity is changing they would have to redesign the whole quest encounter as you technically go into a phased version of the city.

Stopping it at the Cinematic with some expanation text of what aheppens from Alexstrasza is a cool idea to overcome the limitation and cost of redoing the whole quest.

[daviddoran]

It is probably for technical reasons, but its also Beta, and they might re-do it for live.