There are three viable paladin builds for solo: paladin/troubadour, paladin/blood mage and paladin/forbidden fist (technically the priest works too, but any class works with the priest and the paladin isn't the optimal choice). There are no specific builds because they follow some simple principles - stack defenses, armor and healing. For the herald you can also see the solo videos on YT for items/stats/abilities/skills. The paladin comes with increased passive defenses (Faith and Conviction), armor and healing (Exalted Endurance, Stoic Steel), while the other class adds more healing and especially pets (which combined with Bardatto's Luxury ability will add basically another 2AR). Some key items are Magnera's Chain (which allows to achieve high resists against all damage types on top of for/will buffs), Lethandria's Devotion (main shield giving more healing and defenses), Wintertide Bulwark (backup shield used for the deflection buff which stays the entire fight even when you switch to another shield), Cadhu Scalth (backup shield used for increased deflection, damage reduction and modal). For weapons - Bardatto's Luxury, Modwyr and Animancer's Energy Blade.
Another key element to these builds is stacking resting bonuses. For example, the herald can achieve over 170 in all defenses, 19+AR and heal 40+hp every 3s, which makes him virtually unkillable.