By Christine Chen and Scott Murdoch SYDNEY, Dec 3 (Reuters) - The Australian Securities Exchange's technology turnaround plan, touted by the firm's chair as being too important to fail, is facing questions from investors and market participants after it was hit by a fresh outage this week, the ​latest in a string of failures. About 80 companies with price-sensitive disclosures were placed in a trading halt on Monday after the ASX's announcement platform ‌collapsed, leaving hundreds of statements unable t ...