Wheeling Thrust and Fang&Claw should be learned together at 56 would absolve all of these issues. Let's propose fun ideas for a real level 58 ability. I'm thinking support/utility abilities that don't buff DPS per se but enhance either debuffs or our AoE rotation:
Camlann's Torment:
Delivers an attack with a potency of 100 to all enemies in a cone before you.
Combo Action: Ring of Thorns
Potency: 220
Additional Effect: Slow
Gives a bit more oomph and a third combo to the seemingly short HT>RoT combo with a nice little slow effect. Tricky to setup due to HT>RoT's positional requirement..otherwise Doom Spike is probably still better.
Angon:
Delivers a ranged attack with a potency of 100.
Combo Action: Piercing Talon
Potency: 190
TP Cost: 150
This would be a neat little boost to ranged DPS for mechanics where you need to stay out of range but maintain damage i.e. Ravana's Surpanakhas or other kited fights. Huge TP consumption wouldn't detract from MCH or BRD range DPS.
Drakesbane
Delivers an attack with a potency of 100.
Combo Action: Feint
Additional Effect: Blind/Gravity
This would give a bit more purpose to Feint and an option for DRG to have some form of crowd control. Feint is usually used in low level situations because 20% is potent, but having it weigh a target down and blind it, it helps decrease incoming damage further.
Again just one of these would be better than getting Wheeling Thrust at 58. We're already strong enough in single target DPS, giving us a slight boost for situations where we need crowd control in 4 man dungeons (if healer or tank dies...it'll go well with Keen Flurry), a boost to ranged DPS for mechanics where we DPSing in melee range is virtually impossible (albeit at an extremely high TP cost), or a slight boost to our AoE damage by adding a 3rd combo to HT>RoT combo, because DS is only 160 potency...damage barely ever tops half of what a single Holy does.
Highwind
Delivers a jumping attack with a potency of 300. Returns you to your original position after the attack is made.
Additional Effect: Reduces duration of Blood of the Dragon by 30s.
Another option is an ability which COMPLETELY negates BoTD time no matter its duration, but does big damage. For those moments where BoTD has 1-2 sec up before you can refresh it. If doing a proper rotations, technically Geirskogul would still be better as you could do 3 per 60 sec, whereas Highwind would consume the whole effect entirely, which makes it only good as a last ditch spike in damage. BoTD wouldn't buff Highwind by 30% nor would Power Surge affect it either.