Well, its more about synergy. Brummbar as first tank will suck but when you combine it with AT, its amazing. It denies infantry with at nades, it can deny at guns etc. Brummbar+Panther is better option than 2 Panthers.
Synergy is always good. but i find the ostwind + panther a better synergy as the ostwind has the mobility and turret to tag along with the panther when its flanking.
If i compare this unit to all the AI tanks in the game this one is the worst for cost. i either it needs a buff or a fuel reduction. its not that this unit is worthless far from it but simply provides far to little for such a price tag.