First off, industrial relations is considered a specialized niche in HR and definitely not under admin. The fact they offer you 3.5k with only 2 yrs work experience is proof, admin HR Executives will take at least 5 years to reach that kind of pay.

As a specialization you don’t need to worry about pay prospects, it will definitely be higher than normal admin or marcom. With 5 yrs exp should reach 6-7k on average.

Having said that, not everyone can do IR. As your stakeholders are blue collar workers, union laborers or junior white collar, you must be comfortable interacting at their level. This means dealing with a lot of minor issues like complaints on uniform, cafeteria menu, shift scheduling, personal family matters, discipline issues…

This is an area a lot of BPs find it beneath their stature to deal with, so you must be accustom to handling such things. Balancing between management & union interest is challenging & sometimes politically dangerous.