Actually, I think I understand what you meant by "performance indicator". Inasmuch as a higher bhp figure is an indication that a car develops high torque at high rpm then yes, it is a good indicator of "performance".
But let's not forget that this is all in the context in which it was intended. The rate of acceleration is only ever governed by torque. Ever. The rate of acceleration is what makes a car feel quick to the driver, it is all we're aware of in terms of straight line performance as a driver. A car like the 30D will always feel quick in any gear whereas cars like the 335i and M3 will never "feel" as quick because they can never have the same amount of torque applied to the drivetrain. Thanks to gearing, they will be empirically quicker when driven in the higher rev ranges where they shine and as I've always said: they'd leave a 30D behind but again, nobody drives like that in the real world and they have
to be driven like that to be as quick as a 30D - and will never feel
as quick unless you're booting it at 7000rpm in third or something: an experience you can't match in a diesel.
So since these kind of cars require effort, revs and a lot of fuel to match the 30D's performance and even more to surpass it, in the real world of on-road driving, the 30D is the quicker car and torque is more important than horsepower.