No, I don't think of it as an anti-tank platform. Also, it's unhealthy for it to drive directly onto a flag and fire around itself because the 25pdr packs enough punch to damage itself, unlike most other HE shells. I think of it (in addition to mobile artillery) as an area denial/suppression weapon. Park it outside a flagzone and start raining death. If friendlies arrive to actually take the flag, it's a bonus. Also, you don't have to worry about ammo selection, unlike with Sherman or Grant - you can fire HE all the time.
As for rolling, I have managed to roll a Churchill over, so even the Marder III feels a wee bit top-heavy for me...