Panther is not terrible when defending, but what do I do if I want to attack? You cannot just defend, you need to attack to take territory or take down those Katyushas, and if they have heavy tanks like the ISU-152 I need to be aggressive and flank it if I want to deal with them.
In such situations at least I personally feel like it doesn't offer me more than a cheaper medium tank would. It has only slightly more health (or not even that compared to a T34/85), the range doesn't help much here and you can not really ensure that you get only hit in the front on such an attack.
If you have advice how to make a Panther work well in the offensive I would like to hear that.
It's not the role the panther fits best in game, but it's still a fast medium with great pen. If you want to flank with a panther, it's never a good idea to do it long and wide- too much risk of getting snared and dying for you to throw it away like a cheaper tank.
Your best option is to engage frontally and try sneak the panther in edgeways- close enough to your actual lines to be defensible if it does get snared.
Aggressive panthers, though, are not aggressive in the same way that an IS-2 is. Never lead with your panther- lead with infantry and AT guns and whatever else you have and have the panther keep stride with them. That 50 range is not to be under-estimated; it means other tanks cannot engage you or your infantry without getting shot back at by the panther midst the troops.