If you receive 100 ms worth of traffic in a lump and buffer them all then the last packets to go out will suffer a 100 ms extra delay (just on this link!). Unless you do not care a bit about latency, you do not want that. What you want is to drop a large number of these packets so a similar burst does not happen again.
Note: since TCP is ACK-clocked, it is not bursty at all.
> In general, the proper queue size grows with the RTT of the flows,
I do not see why. The RTT matters only for end to end buffers.