Well Alter Bridge is my favourite band, but I understand why some people might feel that way. The songs are similar in that most of them have a similar structure, and often use a similar type of chorus.
While I wouldn't mind seeing some different songs, like "a 10 minute epic" (which I would love to see Alter Bridge try), the fact is that mostly bands having too much "variety" on their albums usually just means some of the songs flop, for me. I don't think every Alter Bridge song sounds the same, or even too similar, at all, but I can understand that many of them aren't drastically different. I wouldn't mind seeing some different structures and chorus styles, but at the same time I'd rather have an album of great songs in a similar vein than a few songs that completely flop, thrown in just to make variety.
Also I often listen to Alter Bridge songs individually, or at least not entire album at a time. In fact I usually only listen to either new albums whole at a time or concept albums. So for me it doesn't matter if an album has too many songs - the more Alter Bridge music I can get, the happier I'll be. It probably doesn't help people listening to the whole album and finding it difficult to get through that they're probably hearing the American version with two extra bonus tracks - 16 songs is quite a lot to get through, especially when a lot of the songs are of a similar type.
That said, I think AB III is an amazing album, every song on it is great and many are absolutely amazing, and although I might like to see Alter Bridge do some different song structures and more choruses that are a bit different, the fact is Alter Bridge have always made the best music for me, regardless of whether I prefer less standard song structures, and in the end the music will always win for me over variety, being experimental or having non standard structure.