well, there could be plenty of reasons...
1) try azureus 2.5.0.4 as there are blogs/posts which i read that many sites have re-allowed azureus 2.5.0.4 as the new one is CRAP.
2) try optimizing the incoming/outgoing connections for your connection... I usually keep it as 250/500 (in utorrent).
3) try encrypting ur traffic
4) did you try downloading with private dedicated trackers.. if not, try'em. If you get good speeds there, then its just that the public tracker was relatively less effective, the swarm speed was just not sufficient.
5) Also check if your NAT is ok... if not, you will have to contact BSNL and ask them to allow or open certain ports for you and you should use those ports...
Have you tried any/all of these? if not, please try'em and post back.
as for your question reg. what settings to use, you will get all the required information here, just in case you need them... *www.azureuswiki.com/index.php/Find_best_settings