This is just a list of skills that you never really see used because they are underpowered or just overshadowed by other skills. I am still hoping one day Anet will take a good look at these skills and make them interesting again. (this list is just from personal experience, if you think one of these skills is actually used more often feel free to correct me).
Ranger:
1) Storm Spirit: Since vuln is usually capped out on bosses and the active is ridiculously slow, small area and unreliable, this skill is very underpowered.
2) Water Spirit/Spirit of Nature: Same problems as Storm spirit: passive isn’t strong and active is slow and unreliable.
3) Muddy terrain: been a while since I’ve seen this used. Purely immob/cripple field isn’t very fun or effective to play.
4) Sick ‘Em: This skill actually isn’t bad. The pet is just bad. No use buffing pet dmg if it can’t hit moving targets.
5) Frost Trap: Since trapper builds are usually heavy condi-dmg builds, a trap that only inflicts chill isn’t preferable to a trap that deals dmg.
6) Glyph of Unity: this skill is just extremely underpowered. Probably the worst elite in the game.
Elementalist:
1) Signet of Stone/Water: These skills aren’t actually bad compared to other signets in the game. They are just overshadowed by the other options ele has and lack flavour.
2) Conjure Flame Axe/ Earth Shield: While Frost bow is usable and Lightning hammer can sometimes be useful, these 2 conjures are just utter crap.
3) Glyp of Elemental Power: Low proc chance, 5 sec internal cooldown and only the burning from fire could be useful.
4) Tornado Elite: Transforming in a tornado isn’t really usefull if it means lower dmg and no increase in survivability.
Thief:
1) Ambush: Summon an npc that deals super low dmg, how very useful!
2) Thieves Guild: same problem: the thieves are just underpowered.
3) Ice drake Venom: 4 seconds of chill isn’t all that great.
Guardian:
1) Spirit Weapons: While the sword can be usful in pve burn builds, the other weapons are pretty bad (bad ai) and have too long cooldowns. Also only the sword actually gains the burning benefit from the trait, whose idea was that?
2) torch #5: while torch 4 is very strong, torch 5 is basically a wasted slot.
Engineer:
1) Med kit: have you honestly ever seen someone use the med kit abilties? The only thing useful about it is the toolbelt heal, the kit itself is terrible.
Warrior:
1) Banner of Tactics: healing power isn’t really useful (bad scaling) and the other banners are just a lot better.
Mesmer:
1) Illusion of life: Yeah basically none of the other revive skills like this is ever used, but this one is especially bad as it doesn’t even fully revive allies
2) Phantasmal disenchanter: never good enough to sacrifice a phantasm slot.
Necro:
1) Signet of vampirism: I guess it has a pretty long cd for the effect.
2) Flesh wurm: It’s immobile. And while it should theoretically do the highest minion dps, it performs worse than shadow fiend.
3) Bone Minions: bad dmg and the explode mechanic is pretty awkward to use.
I think many of these skills could be made a lot more interesting with some slight adjustments. Other skills need a more significant rework (mostly the ones related to AI) What do you guys think?