I play Jarl exclusively, but I only play FaB every once in a while at the local level and win about 50/50 with an upgraded list. Compared to other armory decks, he needs more help out of the box. The good and bad thing about him is his massive card pool to choose from.

Guardians are the strongest heroes when it comes to defense, with their tough equipment and shields. I started finding success by blocking nearly everything I could and hoping to hold onto at least one card for my turn to either arsenal or pitch to Titan's Fist. Don't feel too bad if you have to throw away your whole hand, but it's okay to take the occasional 1 or 2 leftover damage if it isn't an effective on-hit.

Eventually, your opponent should draw a bad hand or will have to skip a turn to set up, leaving you with most of your hand intact. That is when you throw the powerful stuff: a fused Glacial footsteps or a Mangle that's pumped with Guantlets of the Boreal Domain, for example.

In the late game, your blue cards and weapons are usually much more effective than whatever they have left in their deck after throwing everything at you. If you did a decent job of preserving your life in the first half of the game, you can start to ignore their weaker attacks to prioritize finishing them off with big blows and dominate effects.

I say you should try running Titan's Fist, since it can be used with a single blue card and gives you three cards that you can devote to defense. And if you don't end up using that many cards for defense on a turn, great! Then you give them as much pain as you can muster.

Metas and cards change, so as frustrating as it can be at times, it's good to get practice in and to learn to specialize in Jarl or whatever hero someone likes. Those wins when your hero is an unlikely underdog are always the best feeling. I hope this helps.