For me, Obviously the biggest changes would be on how the Authority was presented, who they were, and how they conducted themselves this season. I wouldn't have been so quick to introduce them as the writers did, so as to preserve their air of mystique... if anything, I'd have it run the same where Bill and Eric manage to escape, but the authority is kind of content to let them run wild for a bit so as to watch them... Bill and Eric would think they're fine and in the clear, when really they're being watched or monitored. This presents the opportunity to keep Nora as a double-agent, only her double-cross later would be far more dramatic since it would seem she helped them escape in the first place.
Since we heard about Salomé's involvement as early as last season, I'd probably make her the big bad for the season, but I definitely found her to be portrayed as rather unthreatening thus far. Her character would have to be completely rewritten. I think they tried to pass her off as some master manipulator who could get whatever she wanted from anybody with her powers of persuasion, but so far I've seen Eric, Bill, Maryanne, and a whole other slew of characters from the show fantastically outclass her in this regard. She's no Palpatine, that's for sure. That dude was manipulating both sides of a galactic war, setting up things decades in advance just to raise himself to power as supreme Emperor... If Salomé were such a world class seductress, to be honest, I expected something of the same calibur from her. I'm not saying we should've seen her manipulating the Authority AND the sanguinistas at the same time, with her true motives hidden until the very last episode which side she was really on, but I guarantee it would be far more interesting than seeing her flounder as this seasons big bad altogether.
Russel should not have quickly recovered as he did, and he still should be missing a fang! They said it takes 5 years for fangs to grow back, and here he is a year later with both of them intact. Just sloppy. I'd have him weakened from his previous glory as such, and would have put him on the run from the authority to showcase how powerful they really are (or rather, SHOULD have been.) This would put him in a "friend of my enemy is my friend" situation with Bill and Eric, which would have been way more interesting and dramatic to watch, seeing as how both sides would be unsure if they could really trust the other. I also dunno what they plan on Russel's fate being by the end of this season, but I would have him killed in the final episode, in a fantastically easy gesture at whatever is meant to be the big bad for next season, be it an older vampire or some other supernatural creature.
Let's talk about Sookie and the fairies a bit. I'm not crazy on the whole "don't use your power too much or you'll lose it forever" bullshit. Clearly her abilities are a biological trait, and while you can exhaust yourself without enough rest or time to recover, saying she'll "run out" of energy to produce is like someone telling you that if you spit too much you'll eventually run out of saliva. Sure, you can use up a lot spitting on the street or whatever, especially if you did it constantly, but drink a glass of water and rest up for a few hours and your body has replenished itself.
I would have put more fairy presence in this season than the last. It seemed like when they were introduced in season 4 for their brief period, the fairies were being set up to be a very credible threat down the line, (they were instantly able to disintegrate somebody like nothing) but this season it's kind of like... wtf? They have a strip club? Okay, cool. Is it an evil strip club with an insidious purpose? No? Just a safe house? LAAAAAAAAAAAAAAAAAAAAME!!! Do something with these mystical creatures, for christ's sake... They're allegedly very powerful and mysterious, don't relegate them to being little more than strippers. Have them infiltrate humankind, have them enchant people or try to corrupt Sookie. Have them be mischief causing trouble makers, casting spells that curse or ruin peoples lives... I was expecting a lot more from them this season and all my expectations with them kind of fell flat.
Also, Rather than Terry and Arlene dealing with this whole ifrit nonsense, I would've found a way to stick them into the fairy storyline (probably making them victims) so as to keep the pace of the show more focused on just two primary storylines, and Sam, Luna, & Alcide would've kind of oscillated between the fairy storyline and the vampire one.