Some of the perks seem weak so few players bother selecting them. I think some minor adjustments would make them more desirable.
Taunt: rarely taken perk since doesn’t help kill enemies, or even reduce their damage output, just causes them to switch targets. 4 AP/15 fatigue also seems fairly high. In comparison, Shield Wall is 4 AP/20 fatigue.
I have it on one of my tanks, but seems too situational. Tanks are already highly fatigue-constrained so he can rarely use it, much less justify it over Shield Wall, just to divert an attack or two from a 2H merc.
You could reduce the cost, particularly the fatigue amount, but I think the better option would be to make the debuff last longer. A duration of three rounds, but limited to one target (ie. if you Taunt again, the previous target loses the Taunt debuff) should be balanced and a worthwhile expenditure of the fatigue.
Adrenaline Rush: reduction in fatigue cost to 20.
Bags and Belts: a further reduction by half (rounded down) for the fatigue cost of all items in bag slots, so now only quarter fatigue cost. Alternatively, no fatigue cost at all for bag items.
Fortified Mind: increase to 35% since resolve is a weaker stat.
Mace Mastery: Knock Out will stagger if target is stun immune.
Hold Out: could probably also use a small buff, say a bonus to morale checks when taking hp damage, or a slightly reduced chance to get an injury.