Bad. Some people are really jazzed on SuperStannis, but I think the condition on his ability is too onerous to get excited about – I don’t want to be at a “permanent” disadvantage to get +1 combat strength in a single battle. Until the endgame, when you want to march last anyway, I'd rather have turn order priority even if it makes my 4 card a blank. Davos and Brienne are two of the better 2 cards (Roose and Balon are miles better, but play so “unlike” their printed combat strengths the comparison feels unfair). Salladhor is a great 1 card, and Patchface is a unique weapon/deterrent, but at best Salla is 2nd best in his rank and Patchface 3rd. Renly is not good, and Melisandre is one of the most useless cards in the game.
Baratheon is bad at both inflicting casualties and defending against them, as they only have 2.5 swords, one of them is almost completely useless and another shares space with their only fort. Patchface can be a real blow, but the nature of Martell and Lannister’s 0 cards means you have to be cautious about throwing him around willy-nilly. The deck as a whole just doesn’t do any particular thing very well. Tyrell manipulates the board, Martell kills units and momentum, Lannister manipulates you into exposing yourself, Stark survives and strikes back, and Greyjoy overpowers you directly. Baratheon is just…kind of there. They have a lot of strength pumping abilities like Greyjoy, but with far more stringent conditions. Stannis needs you to allow yourself to be raided first every turn. Davos needs you to fire your biggest gun early. Sallador is best on defense at sea, which is not a situation you can engineer yourself.
It's also pretty bad at baiting high cards from opponents, in spite of Patchface's ability to compound the card imbalance if an opponent overplays initially, because it lacks forts to protect itself from the swords of Edd/Viper/Gregor. And it is highly susceptible to bait itself, since opponents don't give much of a shit about losing to Stannis or Renly if it comes to that.
KEY CARDS:
Sallador Saan. He is what keeps Martell from simply wearing you down and taking Shipbreaker Bay every game. Just be mindful that he will cancel out allied support as well as enemy strength.
Patchface. The only truly unique weapon in Baratheon’s arsenal. The best times to use him are when your opponent has 7 cards or 1 left (so you can avoid a card – probably Doran – for an entire hand cycle). Though in a pinch you can attack them when they have 3 left, to use him as a version of Tyrion, forcing them to leave a power card as their last, and not get it back on the redraw.
The other question is, with full hands, who do you discard? Against Stark, Roose is the prime target. Against Lanni/Tyrell, I am usually more afraid of their 3 card abilities than the 4's strength, but either are fine. Against a savvy player, I will pick Queen of Thorns more often, as that old broad can cause no end of trouble if her handler has some imagination. Against Martell, it’s frequently a bluff that will either draw out the Viper or Doran if he is calling you on it. I’d generally just toss whichever he doesn’t use, though sometimes Arianne makes the most sense if you have a powerful enough march lined up to take a difficult territory.