Holy slayer is really versatile as a tank/dps hybrid. Some ideas to consider:
Tutillos(sp) palm is not just for monks. Pick up dual wield AND shield styles. While technically weaker than a real weapon, the extra strike let's you get a second chance at applying ability effects. You will benefit from both the deflection from shield style and the speed boost from dual wield.
Flames of Devotion is a full attack that counts as a fire ability. Itemize and build with this in mind. Scion of flame, ring of focused flame, etc.
All of the paladin orders work great for this kinda build. My favorites depend on mode:
For tanking in a group I highly recommend shieldbearer. With that, shield, and persistent distraction you will get 3 engagement slots. The better version of loh is great too. Exalted endurance to help with party heals as well. You will do decent damage, help with healing, AND tank 3 mobs all at once!
For solo I would go goldpact. Since you won't have a party to "tank" for, the added armor is more useful. Shieldbearer was nerfed so their death prevention on loh is party only. Bleakwalker also is worthy. Your FoD will afflict enemies and do more damage. Definately pairs well with ring of focused flame and scion of flame.
Brand enemy, gouging, arterial, and ring the bell for maximum damage over time on one target. Pick up serafens hand mortar (like in my holy hand grenadier build) and you can apply gouging and arterial in an aoe. REALLY strong.