The problem with C.Tiger's aura is not that it is a "Small timed buff" but that it cripples the DPS of the C. Tiger itself, which is probably the main source of damage in one's army composition. In other words it does not actually improve the damage army dishes out...
Imo the aura of the Panther should be separate into:
Always on that could be the vet 1 bonuses
vet 1 active ability timed aura the vet providing the vet 2 bonuses
vet 2 a bonus in the aura it self like lower cost or longer duration or sorter CD
The rest of the vet bonuses can remain but affect the "ability"
That would it allot easier to balance the aura and thus the unit.
Noone is going to bother revamping the Cmd Panther’s aura, therefore I propose a small veterancy gain buff via extra inf damage to help make the unit relevant again. Much easier to implement and balance.