Quick question about this career. I've noticed that some influence talents have restricted career requirements but apart from a few that allow any career to use them there are none specific for the Crusader career.

Is there a reason for this ? and do you think it lessens the career not to have any?

Most probably, the reason comes from the Crusader / Hierophant relationship: the ones that would be axclusive to one of those, are included in the other (faith-based talents for example). Meanwhile, the Crusader also has a relationship with the death cult assassin (melee) or the Storm Trooper. It's a paladin, after all, and paladins are mixed breed of pure clerics and pure warriors (usually).

Crusaders seem fine to me, they don't have Influence talents because that's not their job, if you feel your character should have a particular Influence talent because of his character history or whatever petition for an Elite Advance, it specifically says that you can take Influence talents as elite advances, or even be awarded one through roleplaying for free.

If you want a hard done by Ascended Career, look at Storm Troopers, they really got it in the balls. Bland and restrictive career abilities (Hellguns with the Tearing rule are nice, but other careers get much more useful and interesting options), very few special talents or exotic skill groups, and a ton of their important skills must be purchased individually for 700XP at +10 and another 700XP for +20, instead of paying 400-500 apiece for the Mastered Skills they come from. Harsh.