Wanderer Firebrand Axe & Shield / Spear GW2 Firebrand WvW Builds
Firebrand is the Guardian whose virtues become books. 
Tome of Justice is the offensive one, 
Tome of Resolve the healing and cleanse one, 
Tome of Courage the 
Aegis and defence one — each opened for a handful of pages and then closed again. That is the spec's whole character: its output is a resource you spend and regenerate, not a cooldown you press. The mantras work on the same idea from the other direction — prepared in advance, then cashed in when the push lands. 
Mantra of Liberation grants 
Stability and 
Resolution and breaks 
Stun, 
Mantra of Solace heals, 
Mantra of Potence quickens the group.
We run two of them. The Minstrel's support is the squad build: no offensive stat on it, everything spent on Stability and boon duration. The Wanderer's hybrid drops Honor for Zeal and takes power on the same gear, so it is in the bomb and still handing out boons — worse at both jobs, useful when you are a body short. Luminary covers the same support slot with a different mechanic; Firebrand is the pick when the squad wants tomes it can open on demand.
2 Firebrand builds
Wanderer Firebrand Axe & Shield / Spear Boon Firebrand Spear / Staff Playing Firebrand in WvW
The tome is the mechanic and the page count is the cost. 
Purity of Word turns your three virtues into tomes and gives you mantras; pages regenerate on their own every few seconds, and the support traits exist to speed that up — 
Archivist of Whispers gives your virtues three more pages, 
Loremaster generates them faster, 
Swift Scholar refunds a page every third tome skill and grants you 
Quickness for equipping a virtue.
What the build asks of you is bookkeeping under pressure. You are pre-charging mantras before contact, spending pages on the right tome at the right moment, and dropping 
Hallowed Ground where the squad will be rather than where it is. Nothing on the bar is instant-and-forget. Where it struggles is when it is caught out of position: your Stability is on cooldowns and charges, and once they are spent, a full Minstrel's Firebrand has almost no way to threaten anyone or leave. You survive on toughness, vitality and the squad staying on top of you.