Although I am sure it is very relevant to study the ratio pax/crew, I feel it is all relative to the level of service offered.
Economy passengers are provided with a less demanding service than business or first class Pax.
Since it is BA's policy to aim at the premium class passengers (since 99), it seems that they have indeed upgraded the service offered on board. I am sure we all appreciate that it is far more quicker to give away simple trays with orange juice/water inculded than offering a choice of meal, bread, wine,... to each individual seating in Club or First.
That said, what do I know but that's a thought.