The effect will be exaggerated since tor traffic goes through three nodes and random jitter would need to be added for each. In general, beating traffic analysis in a low latency network is a hard problem. You could have perfect anonymity if you could add arbitrary delays but that would make the network unusably slow.
So make it a configurable option that you can turn on and off when you need it.
Having to wait a few seconds for a web page to load seems like a small price to pay to avoid government agents banging on your door because you're looking at "subversive content".
The delays would have to be longer than that, not just a few seconds. You're looking at minutes to hours for strong guarantees. Also having a configurable option could make you more fingerprintable.
