I also noticed that some bidders place multiple bids in same round. Some of them even do this at a long time before the end of the round.

In my opinion, the strategy to use multiple bids to scare off potential bidder is far more effective in the last minute. If I found bidders placed multiple bids long time before deadline, they are just normal early bidders to me. Sometimes, I even wonder if they are newbies who don't know about T11 auction and care even less about them.