So is no one having success with house tyrell? I admittedly haven't played many games as I don't play OCTGN and have been rather busy in my personal life.
I'm having lots of success using 12-14 of them as banner-men in other decks.
Margaery, Randyll, Heartsbane, Knight of Flowers. A dab of 1g reducer characters (improve setup and pay for stuff) and once in a while bear-and-maiden-fair to combo with things like Pillage.
Queen of Thorns is way less powerful than adding Euron Greyjoy, Balon Greyjoy, Asha Greyjoy and Theon Greyjoy to the 4 above. QoT ability is a joke if you already have played Randyll / KoF (or either of them is dead already) and she's more vulnerable to milks and kneels than the others. Tywin gets knelt, he still grants +2 gold. Euron gets milked, he still has 6 str mil, 6 str intrigue, 6 str pow.
The tyrell locations don't impress me. They're not horrible, they're just again not worth giving up the character advantage of banner-ing tyrell. "pay 1 gold and stand the enemy (so he can fight again this turn still) once per turn)" I find Highgarden to not come close to say Ghaston Grey which is a cannot-be-saved bounce to hand, discarding all dupes forever and making attachments go to hand to be repurchased, and costs the enemy that 6-7g for the main character again.
Or Areo Hotah's version of Highgarden, where you kneel to attack, then he appears from hand, you're not attacking, and you stay knelt and lose a whole turn of your strongest character. Highgarden never stops me from using euron (it can only bounce 1 of my 3 attacks while standing me And costing gold) whereas Areo or Ghaston Grey can.
The Mander isn't a bad draw location, but I find it no better than that Great Kraken I'm getting by running the not-bad Tyrell characters inside my greyjoy deck.
Left+Right would be a bonus if they weren't Uniques. If you run 6x of them then you risk lots of dead draws when they inevitably claim soak or eat wildfire assault. If you run 1x of each, they'll very rarely get their ability, and still normally be broken right up by wildfires as soon as you get 2 4g+ characters out. (If you kill a 4g+ character to keep a 3strength one, then opponent wins anyway so that's not an option. Particularly because 3str won't let you proc your card draw location like having 3 real big ones on board)
I think they definitely have some promise going forward into the future, it all depends on them getting lots of new expensive characters for QoT to bring in. If Randyll's already on board but then you get a new Renly Baratheon from some chapter pack (assuming 7g strength, 6g min) in hand, then QoT ability might become not so horribly situational. Each chapter pack, they should, hopefully, become less unimpressive.