Ok, I guess I will be the first one.
I will try to list all the skills that right now never get used, and why:
Acid Shell/Fireball: These spells cost 3 memory points and they feel like weaker versions of their memory 1 equivalents. A fireball inflicts pretty much the same damage as a firebolt, but cannot crit, can be halved, costs a lot more mana, has a huge cooldown and has a longer casting time. The only advantage of the fireball is the higher amount of stacks and the area effect, but honestly even if both fireball and firebolt were memory 1 spells I would struggle to believe many players would go for fireball. Similarly for acid shell. Both of these spells need a bit of a push. Fireball for example could easily be a spell with an INT*30 damage and 60 stacks that decrease with the distance from the center, to make it more interesting.
Cloak of whatever: Cool idea, but for the amount of damage and stacks they inflict, 40 mana per second is really too much. It could be lowered, but IMO these skills would be far more interesting if they were a bit more dynamic. Very low activation cost, like 50 mana, short cooldown (4 secs) and instant activation. Keep the 40 mana per second. This turns them into something that you need to activate and de activate as needed, at which point they become very interesting skills.
Acid Arrows/Burning Arrows/Chilling Arrows: Yeah, it feels weird to put them on the "UP skills" list, because they are used by pretty much 100% of the archer builds. But let's be honest. Would we still use them if it wasn't to circumvent the strike wounds bug? Is an INT*2 additional damage really worth the 50 mana of the arrow? Maybe the chilling arrow because the chill stacks are indeed useful, but the burning one? I feel like they could easily be moved to 30 mana per arrow.
Elemental touches: Same as arrows. Really too much mana required to be used effectively. Fists have also an higher attack speed than arrows, so they will drain you really fast. Ideally, I think that both arrow and fist skills should be changed in the way they work, they should be a cast which provides your next [INT] arrows/ [INT*1.5] punches with the effect. Too many toggles are boring, and they don't interact with the "casting a spell" effects. But that would actually require reworking the skills, so just reducing the mana cost would be a faster fix.
Ricochet: This skill has simply no application or purpose. It costs mana, is used in niche situations, has not so interesting effects and the arrows don't carry any of the base attack effect. They can't even crit. I can't see a situation where an archer would put this on his bar. A possible way to change this skill, is by making the projectile stronger the more it bounces. 50% damage increase on each bounce? Auto crit on bounces? Adds 50% of the damage to the first target as pure damage? There are many possible ways to make this an interesting skill, and they mostly depend on making it an attack that you aim at someone which isn't your primary target, so that the bounce hits your primary target for additional effects.
Volley: Similar applications and issues of Ricochet. It doesn't have a real application. It can technically be used in some particular builds as a shotgun shell, but in reality it is just never used. It should probably get an additional effect on those projectiles. Fear? Confusion? Strip buffs? Lower armor? Lower evasion?
Energy blast: Useless in pvp due to the long charge time and equally useless in pve since in 4 seconds I can do more than INT*32 and for surely less than 400 mana. Cool idea, but the channeling time should be halved (and it would be nice if there was a visual effect where the blast is charging).
Static discharge: Worse version of energy blast. This one is even player centered, 3 memory points and can hurt your allies. This skill can't be easily fixed with numbers alone. It should probably become a spell like explosion, just self centered. You activate it, and 4 seconds later you release the discharge. No need to channel.
These are the skills that currently really feel like they need some help.
There's a lot of other skills which are very rarely used right now, but they are mostly tiered to big fights which we have not seen yet, so we can't judge them properly.
As for actual UP builds, I don't want to speak about that yet, but I can for sure name one. Bleed and poison builds. Really nice effects and potentially strong, but as long as the remedies work like they do and as long as they can be used from inventory, these builds will never have a place in pvp.