Tirion Fordring will not be in the designated area of Crusaders' Pinnacle if you have not completed the questline to unlock it. First, speak with Highlord Tirion Fordring in the Argent Vanguard to accept the quest Honor Above All Else. This will open up:
Phase 1
1.) Scourge Tactics
2.) Curing the Incurable
3.) Defending The Vanguard
After all of those quests are completed If There Are Survivors... will allow you to talk to Penumbrius and you'll begin Into The Wild Green Yonder. Once completed, Tirion Fordring will hand out A Cold Front Approaches which will lead to The Last Line Of Defense.
Phase 2
Next you'll be required to speak to The Ebon Watcher outside The Breach in Once More Unto The Breach, Hero. This will once again open up numerous quests which of the following are:
1.) The Purging Of Scourgeholme
2.) The Scourgestone
3.) The Restless Dead
4.) The Stone That Started A Revolution
5.) It Could Kill Us All
These must all be completed to advance to the next of the quests, however they may be completed in any order desired.
Phase 3
The Air Stand Still will open up from The Ebon Watcher. This requires you to kill Salranax the Flesh Render, High Priest Yath'amon, and lastly Underking Talonox whom are all in Scourgeholme. War Horn of Acherus is given for the duration of the quest to make the elites soloable. [Note]: Tag these elites first, don't leave it up to your Death Knight buddy to tank these things. Also keep in mind you can use the Death Knight's Portal afterwards to teleport back to the Quest Giver :)
Father Gustav will then hand out the quest Into The Frozen Heart Of Northrend which will lead to The Battle For Crusaders' Pinnacle.
Thanks, Arjung for the suggestions. =D