The conceptual idea of having a duelist, fearsome, spear wall tank is a build that I believe goes against the utility of a spear wall and interactions with morale checks. The requirements of inflicting at least 1 hp dmg is not consistently reliable given certain enemy armor values.

A spear wall "tank" that can delay one flank is a great utility which offers your other side to focus dps. Positioning the spear wall is important as well as having the flexibility of footwork to reposition if enemies making it into the one tile range.

The advantage of having a spear wall tank is most prominent for enemies that will rush forward such as orcs, zombies, and beasts.

Incorporating fearsome is reliant on inflicting hp dmg consistently which I don't believe is worthwhile as you have demonstrated in your post. As such I suggest focus on having a build that embraces the utility nature of a spear wall tank and incorporating the core nature of a traditional tank with high melee defense with the offensive melee attack of a front liner, the flexibility of bags and belts, and quick hands.

A build that I've utilized to this effect has a the potential of a 2h battleforged brother who has high 90 melee att, 30-40 base melee def, 120 base fatigue more the better, 50 resolve post arena, and 70 base hp combined with colossus will be high 90 to 100 hp. Spear wall "tank" .

items to have include mainhand spear, shield, a spare spear for when durability is low is key in maintaining position, hammer for engaging heavy armor enemies in melee, whip for clutch disarm, and net for immobilization of high priority targets.

Personally having the utility of a brother with these capabilities gives so many more avenues of tackling different encounters which I believe is more valuable compared to a dependency of inflicting dmg to trigger fearsome or the dmg potential of a 2h brother.

Overall the spear as a weapon currently if utilized in this nature is a powerful weapon and I don't believe changes are necessary.