I dont know about rating french lines by dangerousness...im not a fan of nc3 anyway in the french and if anything it seems to just hand black strong queenside counterplay frankly.
Sure, 3.Nc3 isn't everyone's cup of tea, and the Tarrasch is a good and very respectable positional approach against the French. But any theoretician as well as any French player of a decent level will tell you that 3.Nc3 is most dangerous, and the fact that it's the main move among high level guys should also confirm this.
The Alpine variation is clearly inferior to the Kilimanjaro attack.