The change and response didn't sit right with me, the title change implies significantly less responsibility, and a much more limited position.
If the pay is the same or greater for less work it sounds like a win. ;)
I declined the offer for other reasons, but is this common practice? Would others consider this a bad sign?
I make a point of declining the moment that occurs and ensure that they understand the reason.
It's worse when they swap your responsibilities after they hire you with no increase in pay.
It is common practice for a small number of businesses, the "what we do is OK with you" mindset. What if the situation were reversed, do you expect you would be hired?
Any lack of direction, misdirection, or loading/unloading of responsibilities makes the advertisement fraudulent or at least poorly composed.
Whenever I've gone back to check 6-12 months later the place has either hired someone quite differently qualified than myself or has closed. Many people report similar experiences at the same places as that's how they conduct their business.
Well run legitimate businesses know what they want, who to hire, and how to attract the right people. No one who's money conscious is going to waste time or risk disgruntled interviewees or employees.
Places that engage in 'unappreciated' hiring and business practices end up with saboteurs and ghost employees.
A ghost employee is someone whom doesn't work for the company but still costs them a lot of money. They are conjured by unfair treatment of former employees or making potential hires run a gauntlet for a chance to find out what the employer has on the table (see the work arrangements and be told the wage range) or find out if they'll be considered at some future time.
Mistreatment of employees or interviewees makes no more sense than doing the same to customers. Word gets out. Check GlassDoor or with your friends and their neighbors.
Check back next year and see if you made the right decision, I've not regretted passing on anyone with shady or suspect practices. Just brush it off, don't get discouraged.