Whether in Algeria or in Mali the prospects of fighting insurgent desert forces requires considerable determination and resources. The two experiences with this in the 20th century, the Italians in Libya and the FNLA in Algeria, prove the point. The Italians in the two Italo-Sanusi wars expended considerable manpower and money in the effort and tried numerous approaches to buy, cajole and exterminate resistance. In the end, massive airpower and armored columns along with a scorched earth policy with brutal murder on a huge scale crushed the rebellion. Algeria's ruling party carried out a very similar campaign of terror and murder to wipe out their problem.
Anyone who thought that the Algerians would negotiate release of the hostages was ignorant of this history. If the French desire to succeed in Mali they have to expect the same tactics and results. In Mali the Tuareg were the top caste of rulers with descendants of Moroccan invaders from the 17th century as another upper caste over an exploited number of castes of lesser privilege and a slave caste. The French conquest did little to change this situation and it is likely that the message of equality of the Ansar Dine is more popular than most Western news outlets are willing to admit. The constant description of rebels as Islamist is insulting and should stop. It would be like calling any fundamentalist rebel group in a Christian country "Christian."
Is there an answer to the situation? Perhaps, the area was relatively peaceful when the Ottomans ruled it. Once the British and French invaded things went from bad to worse and have continued to do so. Will French intervention make things better, I think that is unlikely. Will the Ansar Dine? Hard to say and it is unlikely the Tuareg would, but it is probable that given the great results of Western intervention in Somali and Afghanistan, the people will be better off without it.
See E.E. Evans-Pritchard, The Sanusi of Cyrenaica, 1934. and James Imperato, A Wind in Africa: A Story of Modern Medicine in Mali, 1975 for a bit of history for both areas that are available and accessible for most people.