I went on demiplane and built a level 5 guardian, then compared it with pregen Valeros.

Valeros:
+4 to attack (!)
+5 speed (not sure why maybe a pregen error)
+2 Perception
Bravery
Reactive Strike
Double Slice

Guardian:
+2 AC
Armor spec (2 slashing resist)
Taunt
Threat Technique (7 crit resist)
Tough to Kill
1 extra expert skill (also not sure why)
Intercept Strike
Flying Tackle

These are all the differences, everything else is exactly or at least functionally the same - HP, saves, shield block effects.

In this state, it could have been a champion class archetype. With alignment gone and divine war looming it would make sense to give up edicts/anathema/focus spells for the taunt+threat technique and defensive feats.

I would like to see better survivability to survive Taunt, even more cool shield-based options, and also situational improved mobility to catch up to allies (for example, Intercept Foe granting a speed bonus or allowing to bypass difficult terrain).

Also Taunt being a will save that affects mindless creatures rubs me the wrong way. At least they should get some advantage against it, or maybe there could be a feat to make it a different save type.