Although on other hand, is there any less worse algorithm which already tested on live network?
Not that I currently know of. Loads of altcoins has their own difficulty adjustment, DGW (Dark Gravity Wave) and Digishield are prominent ones, and AFAIK there were different tradeoffs as well. The algorithms are generally designed for specific goals and has different tradeoffs. It wouldn't be applicable to Bitcoin because we don't have huge fluctuations in hashrates. No such thing as less worse, because they are all not good enough if you've got a network that is stable.