For raid content or jobs?

I wouldn't want a PTR done for raids. One of my biggest gripes with World of Warcraft is everything is datamined and battles are solved long before a patch goes live, where as in FF14 everything is a surprise. The PTR for WoW is kinda needed though because they're notoriously bad at rushing unfinished products out the door to meet strict deadlines. The number of bugs that end up live in FF14 is extremely small compared to WoW.

However if you're expecting sweeping job changes because they're playable on a PTR then you'll be greatly disappointed. They might use the information to balance the numbers a bit better and avoid things like the weird monk potencies, but that's about it. If player feedback from live content doesn't get them to rework jobs or make them more complex, why would a PTR? A PTR is pretty much the finished product, they're simply releasing it so players can help them find and iron out any bugs the QA team missed.