I had hoped that Katrina was a voice from the grave and her purpose was to guide the witnesses. In that limited role she worked fine. When they decided that she was alive and trapped in purgatory, it slowed the show down. When they brought her to the present it completely eliminated the uniqueness of Crane's man out of time story.
The first 7 or 8 episodes definitely had 2 co-leads in Crane and Abby, with others in minor supporting roles. I started to become uneasy when Katrina started to be pushed to the fore in the latter part of S1, but I stayed with the show for 2 more seasons, hoping the show would course correct to what made it special at the start. Alas, it was not to be.
Add to that the fact that the actress who played Katrina was not strong enough to play the new part she was given, the train wreck began. Then they cast an even less skilled actress to play Betsy Ross (and once again bring her to the present...clearly not learning from their mistakes) and the damage was done.
I was here for Abby and Crane fighting the apocalypse, with help from a supporting cast. I was not here to watch Crane and the revolving leading ladies (revolving until they found the correct white woman).
What a waste. This was such a fun, quirky, sometimes creepy, supernatural adventure and TPTB destroyed it in favour of a bland, by the numbers procedural. SMH.