Question for you guys. Is there any way to trigger Perserverance before Wicked Hearts or Adamant? I don't want to start Cullen's romance til that starts (since I normally am have the romance triggered at that point, but I wanted to do something different this time around). I plan on doing Wicked Hearts first, but I don't want to miss out on the dance.
It seems it's too late now as you're already doing/done the ball, but... it is possible to finish Perseverance and start Cullen's romance, all before Wicked Hearts. I did this on my current playthrough: finished all his lyrium arc, started the romance, and still got his dance at the ball. You just need to complete the Abyss quest first to trigger his personal quest.
Whether it's worth it... in practical terms, all that happens differently is that he says "You're the Inquisitor... and you haven't always seen me at my best" in the kiss scene. And some of the flirts you get during his quest sound more intimate than if you're already romancing him, weird as that sounds (like the way you touch his chest when you first tell him to stay off lyrium - it's an incredibly intimate touch for someone who's supposedly just a friend at that point, and Cullen's surprised look at the touch makes more sense).
The only real difference is the perceived sense of progression from a friendship to a relationship, though. Like someone else mentioned, it feels less like dating a cute guy and suddenly finding out he's a drug addict, and more like helping a friend through a drug problem and later finding out you're in love with him. It makes the romance pace out slower, so you're not just falling into his bed the second you get to Skyhold, and it makes your involvement have a more solid basis - he initially tells you about his addiction in a very professional tone, but you help him out through it as a friend, and each time you flirt with him through his quests the way he looks at the Inquisitor less like the Inquisitor and more like [your name] is more and more... it feels like you can see him really falling in love with her throughout this process. Whereas starting the romance without this quest, I did wonder where did his feelings for you suddenly come from - you can headcanon that it happened at some point in Haven or through the journey to Skyhold, but it felt more fulfilling to see it happening on screen as you help through his most personal issue.
And it does change the tone of his objection in the kiss scene, of his hesitation to advance your blatant flirting into more than that. It's not just your rank, he's not just thinking "oh it's Inquisitor" - he's embarrassed to have let you see him with his guard down, he's keeping some distance because he's worried that it may have changed your opinion of him. It makes the scene a little sweeter when you're like, yeah yeah you big goofball just kiss me now.
So whether it's worth it or not depends on what you particularly enjoy for storytelling, and how you prefer to see the relationship play out. I personally liked doing Perseverance first a lot better, felt it made the romance more solid, but some people will prefer to go through that after the relationship is already established. But you definitely don't have to miss the ball for it - just do Abyss first, and you're gold.