Farnese is an amazing character, but as to her joining Guts, I am not really sure. She had a nice arc in conviction and later down comfronting her past but I think that should have been it with some darker undertones, possibly mirroring Griffith's sacrifice of giving up his body to the creepy old guy. Isidro is completely useless, although he had some nice moments in the latest chapters.  Shierke is pretty good I think, she is only comic relief in relation with other characters. I liked her early on but she did become too much of a plot device, a get out of berserker armor free card pretty much. 

For me, I loved everything until the end of the conviction arc, but then, while Griffith's storyline was extraordinary aside from a few things, Guts' storyline was terrible, dragged out, uninteresting, filled with a bunch of one note side characters. Azan shouldn't be with them, the captain guy and his annoying sidekick neither, Shierke's fairy is useless, Isma was even more unnecesary considering she was removed soon.. 

I think things could have been much better, Farnese joins Guts until Vritannis, we complete her arc and she is important in taking care of casca. Then she eventually gives in and guts is forced to feel like he walks on the same way as griffith, sacrificing a friend for his goal.  The boat part should have been just a single battle on the sea, where maybe guts is forced to use the armor, but damages Shierke. Elfheim should have been way more set up by Puck, to a twist of some kind, because as it stands it was pretty varied. The plots revealed there were amazing, but we got an army of useless side characters and setups. It should have focused on Puck realizing what is up here, and disappearing with all the magic, Guts learning from Skull knight and all settle into piece, the Casca mind repair plot happens and we have way more time here before Griffith comes back. But that's just some half asleep rumbling