I was playing Nightblade and noted how my eyes had to be glued to the ability bar all the time, even if most of my skills lasted a long time, 20 seconds and up to 32 seconds some of them, so why did this happen?

The problem wasn't the duration of the abilities, it was with every ability lasting a different amount of time, one lasts 10 seconds, another 12, another 15, 20, 22, 24, 30, 32... and that makes it harder to cast abilities with identical timers together, you will always need to break your rotation to cast another ability. Don't get me wrong, longer duration definitely helps, but it is not everything, some changes need to be made.

And I have some sugestions:

A new duration rule that most abilities should follow: Abilities with longer durations must have durations that increase on 5 by 5 seconds, unless the class has other abilities with similar durations and types (dragonknight ardent flame abilities for example). The result should be durations between 10, 15, 20, 30. Abilities that would last 25 seconds should last 20 or 30 to make it easier to manage and find abilities that match each other. This value always includes the bonus from passive abilities that increases duration.

• Nightblade - Shadow - Dark Veil: Remove the bonus duration from shadow abilities and increase duration of buffs and debuffs applied by class abilities by 2 seconds.
  There is no point in increasing ability duration with a passive when you can just add 2 seconds to it. With this, nightblade could also be the only class able to extend duration of off-balance, giving it a more unique bonus.
• Mages Guild - Fire rune: Increase duration to 30 seconds.
  This means you would have another ability to match the 30 seconds rule to use with, for example, Quick cloak or Vampire’s Bane.
• Mages Guild - Everlasting magic: Remove previous bonus, now increases your magicka and stamina recovery by 2% for each mages guild ability active.
  
• Mages Guild - Magicka Controller: Change to increase your maximum magicka by 3% for each mages guild ability slotted on either bar.
  Those changes would make mages guild abilities good for builds that need better sustain while removing the weird durations of the previous iteration, and that would also fit very well into the theme of the guild.
• Two handed - Carve: Reduce the duration to 15 seconds, the first hit always applies hemorrhaging.
  That ability duration increase was nice when no other abilities lasted that much, but it is pointless now. Now, instead of this big duration, it would be a good combo to use with stampede or/and caltrops.
• Dragonknight - Ardent flame: This skill tree may not need those changes because it already has abilities that last the same amount of time and can be cast together.
  
• Dragonknight - Earthen Heart - Eternal Mountain: Now increases the power of damage shields by 10%.
  Duration of other abilities should be adjusted to match the new duration rule, Ash cloud should last 20 seconds and molten weapons 60, maybe with a shorter morph that turns your physical damage into fire damage or something, but that should be another topic.
• Templar - Dawn's Wrath - Enduring Rays: Instead of increasing the duration, increases the power of Dawn’s Wrath abilities by up to 20% after half of their duration. Readjust damage values of some abilities to be in line with previous iterations.
  That would give it extra power for the final seconds of each ability but players would still have time to react from those empowered beams. It would also encourage players to make those abilities last the entire duration and make the passive more relevant for this skill tree.

But there is also another thing that helps creating easier rotations and ties well with the changes I suggested, that is, skills that last 3 seconds. Those skills are good to maintain rhythmic rotations and although not every class needs to be that way, it is a perfect combination with warden and necromancers. You cast Blastbones and 2 abilities together, then Blastbones again and other 2… You don’t really have to think much about this, you just follow the rhythm, but in order for this to work some changes would have to be made:

• Necromancer - Grave lord - Blastbones: You can now always cast a second Blastbones after 2 seconds, but the last one will self destroy 1 second after calling another.
  This would just make the ability reliable for all ranges, the only thing it needs.
• Warden - Animal companions - Subterranean Assault: Stir a bigger group of shalk that attack after 3 seconds, dealing 3600 Poison Damage to enemies in front of you. After the shalk complete their attack, they burrow underground for 3 seconds and then resurface again, dealing 1800 Poison Damage to enemies in front of you. Cost is reduced if cast before the second attack. (Increases number of shalks to 5 to reach longer distances, the first attack to hit deals increased damage and if you cast the ability before the second attack the cost is reduced by 50%)
  This would make it so you can cast this ability after every 2 other abilities to have slightly better damage, but if you miss your cast you still have the second shalk to hit and deal a good amount of damage for no cost.
• Warden - Animal companions - Deep Fissure: Now lasts 20 seconds with shalks coming over each 4 seconds to apply the debuffs. Also increases enemy ice damage taken by 5% to give it a more unique bonus that would fit the theme of the class and better connect this skill line with the Winter's embrace line.
  This morph would have the default range but that shouldn’t be a problem as it should be used on tankier ice staff builds.

And that would be it, the only thing left is to test popular builds to see how easy it is to find skills that fit well together and maybe adjust some other abilities to be perfect. I know many of those changes can be difficult to implement but they would make the game so much more enjoyable so, think about it, and I know that changes like I suggested usually never happen but do it in your way, do your best.