Sanctuary likes to build up enemies and make them look the the greatest threat to Earth--the Cabal and their biological weapon the first and second season, Praxis and Big Bertha in the third season. Ultimately, after all the build up, these enemies are vanquished a bit after meeting Magnus. It's always a disappointing experience, considering how much hype went on in some episodes.
As "Tempus," shows, the writers have not changed one bit. The episode plays out like a trip down memory lane, with Magnus seeing a bunch of stuff from her past without interacting most of the time. It's cool as a viewer to see these things, but the downside is that there little plot in the episode. After lots of hemming and hawing, the conclusion rolls around: Adam kills his daughter, Magnus kills Adam, and Magnus decides to hide in seclusion until the other Magnus disappears into the past. It's a nice, tidy solution to a very complicated problem. Again, Sanctuary has a plot with plenty of premise and then deals with it in the easiest way possible.
The retcon of John not being Jack the Ripper was dumb and pointless. It was already established that John was a killer of some sort, so throwing in the creature didn't change anything. John killed people, the real Jack killed people--so what?