Hi friends! First off, thank you for all the help. I finally got far enough into the main story, I can confirm that you must hit Diamond City and do a few more quests down the line before being able to recruit Paladin Danse. I cannot vouch that my method is 100% accurate, but this is basically the order I played my game in and the choices that I've made;
(I tried to keep this as spoiler free as possible)
1) Meet Danse and a small group of the Brotherhood after listening to a radio broadcast while walking to Diamond City
2) Complete Call to Arms (the first quest Danse gives you). Once completed, you will have the opportunity to join the Brotherhood.
3) Joined the Brotherhood
4) Helped Knight Rhys and Scribe Haylen
5) Received another quest from Danse after helping Haylen, quest given "The Lost Patrol". Now I may be wrong, but I do not believe this quest is mandatory, this is simply the order in which my playthrough led me
6) Continued on with the main story, and made it to Diamond City
7) After meeting a certain journalist, I spoke with a Diamond City security guard posted at the entrance which led me to the quest; "Unlikely Valentine"
8) Unlikely Valentine is part of the main story, you must complete this quest chain. The end of this quest will lead you to Fort Hagen
9) Once finished with Fort Hagen, I was immediately rewarded with "Shadow of Steel". This quest is your ticket to traveling with Paladin Danse.
Hope this helps! I doubt it's needed, but I am currently playing on the Xbox One.