Ostheer hull down gives a firing range bonus, giving the Panther 62.5 range, allowing it to fire back at Allied TDs at their max range.
Which can be useful, especially because with the added durability it can out-DPM up to two Allied TDs with a bit of luck, but it's not that practical because a stationary Panther usually just attracts a bunch of ATGs or artillery and is then forced to move.
Panther hull down can come in handy sometimes, in scenarios like having to defend a victory point to stall out the last few VPs, but most of the time mobility is more valuable than being stationary with a bunch of bonuses. It's definitely not a no brainer ability, which is good.
On teamgame maps, "attracting" a bunch of ATGs usually attracts a bunch of werfers and stukas right back at you. It's definetely not a no brainer ability but there should have been some sort of delay when going OUT OF hulldown (a couple of seconds). The biggest downside is maybe forgetting that your tank is in hulldown and then getting it killed when you think that you moved it. On all hulldowns (allied and axis) there should have been a delay for going out of hulldown. Hulldown bonuses should be about reinforcing weaknesses (range on axis and armour or something on allies) but you shouldn't be able to immediately exit hulldown